The westinghouse air brake, first demonstrated successfully in 1868 : Sentence Correction (EA only)

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

29 Apr 2016, 20:25

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Hi mikemcgarry,

Can you please check my reasoning given below. In addition to your comments, is it safe to consider a 3-2 split in the answer choice based on the usage of 'before' and 'previously'. Once the splits are identified the answer can easily be narrowed down to B because of pronoun error in D.

(a) whereas before they required 5 hand breakers over a distance of 1,500 feet for such a train to be stopped. - Incorrect - 'they' incorrectly refers to freight cars. Also 'before' does not correctly point to the time frame in discussion.

(b) whereas previously 5 hand breakers operating over a distance of 1,500 feet had been required to stop such a train. - Correct - 'previously' correctly refers to the timeframe between 1868 - 1887. Since 'previously' is used there is no need to use past perfect. But there is no real harm in using past perfect here. Also the non underlined part contains had been, indicating the development of brakes from 1868 - 1887. So, the usage of had been seems appropriate here to cover the entire timeframe.

(c) but before stopping the train required 5 hand breakers operating over a distance of 1,500 feet. - Incorrect - before does not clearly point to the timeframe in discussion.

(d) but previously they required 5 hand breakers over a distance of 1,500 feet stopping the train. - Incorrect - Pronoun error

(e) but before stopping such a train required 5 hand breakers over a distance of 1,500 feet. - Incorrect - Same error as option C.

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

02 May 2016, 11:14

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Vyshak wrote:

Hi mikemcgarry,

Can you please check my reasoning given below. In addition to your comments, is it safe to consider a 3-2 split in the answer choice based on the usage of 'before' and 'previously'. Once the splits are identified the answer can easily be narrowed down to B because of pronoun error in D.

(a) whereas before they required 5 hand breakers over a distance of 1,500 feet for such a train to be stopped. - Incorrect - 'they' incorrectly refers to freight cars. Also 'before' does not correctly point to the time frame in discussion.

(b) whereas previously 5 hand breakers operating over a distance of 1,500 feet had been required to stop such a train. - Correct - 'previously' correctly refers to the timeframe between 1868 - 1887. Since 'previously' is used there is no need to use past perfect. But there is no real harm in using past perfect here. Also the non underlined part contains had been, indicating the development of brakes from 1868 - 1887. So, the usage of had been seems appropriate here to cover the entire timeframe.

(c) but before stopping the train required 5 hand breakers operating over a distance of 1,500 feet. - Incorrect - before does not clearly point to the timeframe in discussion.

(d) but previously they required 5 hand breakers over a distance of 1,500 feet stopping the train. - Incorrect - Pronoun error

(e) but before stopping such a train required 5 hand breakers over a distance of 1,500 feet. - Incorrect - Same error as option C.

Thanks

Dear Vyshak,
I'm happy to respond. :-)

My friend, I have no complaint about your logic. The past perfect in (B) is fine. I still maintain that there is something fundamentally illogical about their placement of the adverbial phrase "over a distance of 1,500 feet." I believe what the sentence means to imply is a direct comparison to the 171 feet in the first part: in other words, this is suppose to indicate what the stopping distance of the train was under the previous breaking system. Instead, they way it is currently positions in all the choices including the OA, it sounds as if it indicates where the 5 hand breakers had been standing. It's a very poor and illogical question.

My friend, your logic is fine, but the question is flawed.

Does all this make sense?
Mike :-)

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

15 May 2016, 20:33

mikemcgarry wrote:

inakihernandez wrote:

The westinghouse air brake, first demonstrated successfully in 1868, had been developed to such an extent by 1887 that a train of 50 freight cars traveling at 20 miles per hour could be brought to a standstill in the space of 171 feet, whereas before they required 5 hand breakers over a distance of 1,500 feet for such a train to be stopped.

(a) whereas before they required 5 hand breakers over a distance of 1,500 feet for such a train to be stopped.

(b) whereas previously 5 hand breakers operating over a distance of 1,500 feet had been required to stop such a train.

(c) but before stopping the train required 5 hand breakers operating over a distance of 1,500 feet.

(d) but previously they required 5 hand breakers over a distance of 1,500 feet stopping the train.

(e) but before stopping such a train required 5 hand breakers over a distance of 1,500 feet.

Dear inakihernandez,

My friend, I'm happy to respond. :-)

Official GMAT SC questions are funny. Many times, the OA is a well-written gem, beautifully crafted, but sometimes the OA still has issues but it's the best of the bunch. I think this is such a question.

The opening "whereas" is a much more natural way to create the contrast that the writer is trying to create. The word "whereas" suggests contrast but it also implies a comparison, whereas the word "but" simply delineates a sharp change in the direction of the logic.

Choice (A) uses "they" to refer to the trains and then says "such a train"---this double reference is confusing.

Choice (B) has no pronoun issues, and it uses the "whereas," so it's best of this bunch. This is a rare official GMAT SC question in which I am embarrassed by the poor quality of the OA. It sounds as if the "5 hand breakers" are physically separated from one another over a distance of 1500 meet---that, of course, is not the intended meaning, but that's how it sounds. This entire sentence would have to be re-written to create complete clarity. So, this is a very-far-from-ideal question, but (B) stands out as head and shoulders above the rest, so in that sense, this question has a very clear answer.

Does this make sense?
Mike :-)

Hi Mike,

Thanks for your explanation. I chose wrong option on practice test for the following reasons :

1. I couldn't split between 'whereas' and 'but'. I ignored because both show contrast to some extent. There are other officials problems in which the ans choices are split between words (or conjuctions) which convey the same meaning but may not fit in given context for one or other reason. Any safer approach to avoid such traps?

2. I rejected B because I couldn't rationalise whether past perfect is ok. If the question stem (Without dates/timeframes) demands sequencing of events in past, I still do better. But it gets tougher when the stem involves years/dates etc. I was confused for the same reason.

3. Before/previously - same reasons as 1.

Only thing I could properly use was - pronoun agreement which helped me to reject two choices at best.

Would appreciate your inputs.

Cheers

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

17 May 2016, 02:01

mikemcgarry wrote:

HarisinghKhedar wrote:

Hi Mike,

Thanks for your explanation. I chose wrong option on practice test for the following reasons :

1. I couldn't split between 'whereas' and 'but'. I ignored because both show contrast to some extent. There are other officials problems in which the ans choices are split between words (or conjuctions) which convey the same meaning but may not fit in given context for one or other reason. Any safer approach to avoid such traps?

2. I rejected B because I couldn't rationalise whether past perfect is ok. If the question stem (Without dates/timeframes) demands sequencing of events in past, I still do better. But it gets tougher when the stem involves years/dates etc. I was confused for the same reason.

3. Before/previously - same reasons as 1.

Only thing I could properly use was - pronoun agreement which helped me to reject two choices at best.

Would appreciate your inputs.

Cheers

Dear HarisinghKhedar,
I'm happy to respond. :-)

I will go through your numbers in reverse order.

3) On "before" vs. "previously," notice a subtle difference. The word "previously' is 100% an adverb and nothing but an adverb: its usage is perfectly unambiguous. By contrast, the word "before" can be used either as an adverb (as it is used in these answer choices in this problem) or as a subordinate conjunction or as a preposition.
He came to the house to visit me, but before, I had left to go to the store. = adverb use of "before"
Before he came to the house to visit me, I already had left to go to the store. = subordinate conjunction use of "before"
Before his arrival at the house looking for me, I already had left to go to the store = preposition use of "before"
In this problem, the word "before" is intended in its adverb usage, but it creates ambiguity because it could be understood as preposition:
(C) ... but, before stopping the train, [who?] required 5 hand breakers operating over a distance of 1,500 feet
That opening phrase "before stopping the train" is likely to be understood as a prepositional phrase, and when we get to the verb, we realize, "wait, we need a subject!" We have to go back and re-interpret the word "before" as a adverb and the gerund "stopping" as the subject. This is a very subtle point. Any piece of writing that creates the expectation of one sort of reading and then jarringly forces us to adapt another reading is rhetorically awkward. Good writing fulfills our grammatical expectations in a way that allows the meaning to unfold. That's a problem with "before" in this context.

2) For use of the past perfect, see this blog:
Past Perfect on GMAT Sentence Correction
You will notice that in the example sentence in #3, I used the past perfect, even though there were other indicators of the time sequence. I did so because I was trying to create emphasis: this is a justifiable use of the past perfect even when other elements of the sentence indicate the time sequence. Much in the same way, the sentence in this official SC question is creating this huge sense of contrast between after the air brake vs. before the air brake. The past perfect helps to underscore that logical and rhetorical contrast.

1) This is the hardest, especially for folks for whom English is not a native language---the subtle differences between closely related words. Here, "but" and "whereas" are both contrast words: that is there similarity. The difference lies in the connotation, the quality of the contrast. The word "but" is a 180-degree completely turn around. The word "whereas" is softer, suggesting comparison and connection as well as contrast. I don't know if you have an experience with improv theater: the word "but" is many ways is equivalent to a kind of "no," whereas the word "whereas" is more equivalent to "yes and" (in improv theaters, actors are told to avoid the word "but" and make use of "yes and," to keep the flow of the dialogue going).

How do you learn all these subtle distinctions and connotations? By reading. See:
How to Improve Your GMAT Verbal Score
It is impossible to arrive at GMAT SC mastery by assembling some complete list of differences in meaning. That is a left-brain fantasy that is entirely unworkable. The only way to develop the intuition for the language is to develop a rigorous habit of daily reading.

Does all this make sense?
Mike :-)

Hi Mike,
Thanks a lot for the entire content. It was very helping and insightful.

I would also like to know your opinion on cases which are recommended not preferable on GMAT. Cases like below:

Usage of 'being'
Usage of '[PREPOSITION]+[NOUN]+[VERBing]'
Usage of 'Past perfect' when sequence is clear - our case

All these cases among similar others are not outright wrong but less likely to be correct. They may fit well given other choices are not better. I want to know how should I approach such choices? Should I evaluate the context there and then or skim through other choices first if one fits best? I'm asking this from approach perspective but not a method to minimize my work. Hope you don't misunderstand me in that way. The other day, I spent quality time in figuring out such choices and eventually ended up with lesser than usual accuracy on my sc. Appreciate your help.

Good day!

Posted from my mobile device

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

17 May 2016, 11:38

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HarisinghKhedar wrote:

Hi Mike,
Thanks a lot for the entire content. It was very helping and insightful.

I would also like to know your opinion on cases which are recommended not preferable on GMAT. Cases like below:

Usage of 'being'
Usage of '[PREPOSITION]+[NOUN]+[VERBing]'
Usage of 'Past perfect' when sequence is clear - our case

All these cases among similar others are not outright wrong but less likely to be correct. They may fit well given other choices are not better. I want to know how should I approach such choices? Should I evaluate the context there and then or skim through other choices first if one fits best? I'm asking this from approach perspective but not a method to minimize my work. Hope you don't misunderstand me in that way. The other day, I spent quality time in figuring out such choices and eventually ended up with lesser than usual accuracy on my sc. Appreciate your help.

Good day!

Dear HarisinghKhedar,
I'm happy to respond. :-)

My friend, it is a difficult thing to understand that there is no such thing as a complete list of the rules of grammar. Many students unconsciously want to treat grammar like mathematics and simply learn all the rules. In math, there are clear black and white rules, and one can learn them. In grammar, there are general patterns, but almost every pattern has an exception. Grammar is an attempt to find patterns in the living and changing language, and it always depends on context and meaning.

In all three cases about which you ask, context is everything.
1) The word "being" is often wrong, but about 10% of the time, it will appear as a part of a correct answer. It's extremely hard to formulate a general rule for this. It all depends on the individual cases.
2) For the '[PREPOSITION]+[NOUN]+[VERBing]', see this blog article:
with + [noun] + [participle] on GMAT Sentence Correction
BTW, one way to understand grammar better is to learn the proper terminology. The term "VERBing" is extremely sloppy and imprecise, because the -ing form of a verb can have three completely different roles. In this context, the proper word is a participle.
3) As I have already said, this case depends very much on context. As indicated in my response, one reason to use the past perfect in this case is to create contrast and emphasis. When is this appropriate and when would it be too much? This depends on meaning.

Everything on the GMAT SC depends on meaning. Grammar is trumped by meaning. There are no meaningful rules for grammar apart from meaning. This is why it's so important to develop a habit of reading, so you see sophisticated grammatical forms and idioms in context. There is no substitution for that.

It's almost impossible to discuss some of these topics in the abstract, as if they were mathematics. We have to look at individual sentences. I will ask you to find, posted here already on GMAT Club, sentences that have confused you. In that thread, make an entry and use the "mention this user" button to solicit my input. It's only by looking a specific sentences that we can address these issues properly.

Does all this make sense?
Mike :-)

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

07 Jul 2016, 23:27

mikemcgarry, I suppose usage of "used to" would have been better instead of "had been"?

"...previously 5 hand breakers used to be required to stop the train..."

The use of past perfect tense is kind of preferable for a one time event, rather than for an ongoing/generic fact/habit/process, right?

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

08 Jul 2016, 13:35

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TDK82 wrote:

mikemcgarry, I suppose usage of "used to" would have been better instead of "had been"?

"...previously 5 hand breakers used to be required to stop the train..."

The use of past perfect tense is kind of preferable for a one time event, rather than for an ongoing/generic fact/habit/process, right?

Dear TDK82,
I'm happy to respond. :-)

Actually, either would be fine in this scenario.

All the past perfect tense logically implies is that the action ended before some other mentioned past event. It is not necessarily limited to a one-and-done, one-time event. It could be something that went on continuously for a considerably long time, as long as it ended before another past event.

Most modern humans are accustomed to a night sky without many stars, even since electric lighting became prevalent in the early 20th centuries, although most humans through history had seen a completely dark sky every single night.

That's an example of an action that continued for over a million years, seeing the completely dark pre-electricity sky, but it ended in the past, so the past perfect is perfectly acceptable. It would also be correct to use "used to see," although that is slightly more casual and not as common in formal writing.

Does all this make sense?
Mike :-)

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

20 Jul 2016, 02:12

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The Westinghouse air brake, first demonstrated successfully in 1868, had been developed to such an extent by 1887 that a train of 50 freight cars travelling at 20 miles per hour could be brought to a standstill in the space of 171 feet, whereas before they required 5 hand brakes over a distance of 1,500 feet for such a train to be stopped.

A whereas before they required 5 hand brakes over a distance of 1,500 feet for such a train to be stopped

B whereas previously 5 hand brakes operating over a distance of 1,500 feet had been required to stop such a train

C but before stopping the train required 5 hand brakers operating over a distance of 1,500 feet

D but previously they required 5 hand brakers over a distance of 1,500 feet stopping the train

E but before stopping such a train required 5 hand brakers over a distance of 1,500 feet

I like to compare the differences and here I see whereas vs. but. I’m not very secure about the rule for each, so I’m going to look at something else.

What jumps out is the use of the pronoun, “they.” 2-2-1 split with “they required” vs. “stopping the train” and B says, “5 hand brakes.”
With the use of the word “whereas,” there needs to be some form of contrast/comparison. We need to compare hand brakes to hand brakes. B is the only one that does this.
This is a good illustration on why not to go for style first. Many students would eliminate had been required to stop because it’s passive, but grammar trumps style.
For sake of the full illustration, “they required” : who is they? Hand brake is not a “they” Elminate A and D.
Stopping the train with hand brakers. Hand brakers is not the right comparison to hand brake. Eliminate C and E.

B

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

22 Dec 2016, 08:26

Hi mikemcgarry,
Could you please elaborate more on option "E"? I have to admit that the subtle difference between "but" and "whereas" is totally something new to me;however,apart from this preference,is there anything wrong with "E"?

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

24 Dec 2016, 11:41

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sleepynut wrote:

Hi mikemcgarry,
Could you please elaborate more on option "E"? I have to admit that the subtle difference between "but" and "whereas" is totally something new to me;however,apart from this preference,is there anything wrong with "E"?

Dear sleepynut,

I'm happy to respond. :-)

The "but" vs. "whereas" is more a stylistic preference, not a clear issue of right vs. wrong. This would NOT be the basis of split that eliminated an answer.

The BIG problem with (D) & (E) is the ambiguity of the prepositional phrase:
(E) but before stopping such a train required 5 hand breakers over a distance of 1,500 feet.

Think about it. Where were these "5 hand brakers"? This phrasing makes it sound as if these five men were standing along the side of the track, spread out 1500 feet from first to last, and somehow they would do something to the train as it went by to stop it. Of course, we realize from the prompt this is not the case, but in (D) & (E) we have "5 hand breakers over a distance of 1,500 feet," so it sounds as if the prepositional phrase is meant to describe the noun, and one obvious conclusion is that the 5 men themselves were spread out over this 1500 feet distance.

The other answers correctly have something along the lines of "5 hand breakers operating over a distance of 1,500 feet." That's completely different. Now, it's 100% clear that the prepositional phrase is not supposed to be an adjectival phrase, a noun modifier; instead, it's supposed to be an adverbial phrase, a verb modifier. That's a huge difference. Now, it's not the men who were spread out over that distance; instead, the activity of operating the brakes and stopping the train took place over that distance. This is the meaning that is consistent with what the prompt is trying to say.

What the sentence is trying to say is that the train itself was much less than 1500 ft long, that the "5 hand brakers" were on the train doing their work, and that when those five men applied the brakes, the train covered 1500 ft of distance in the process of decelerating. In other words, 1500 ft is the "stopping distance" of the train. The "5 hand brakers" might have all been in the same car on the train or might have been spread out over the length of the train, but the action, the action of operating the brakes and stopping, took place over this distance much longer than the length of the train. Choice (B) conveys all this flawlessly.

Does all this make sense?
Mike :-)

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

12 Sep 2018, 05:41

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The Westinghouse air brake, first demonstrated successfully in 1868, had been developed to such an extent by 1887 that a train of 50 freight cars travelling at 20 miles per hour could be brought to a standstill in the space of 171 feet, whereas before they required 5 hand brakes over a distance of 1,500 feet for such a train to be stopped.

A whereas before they required 5 hand brakes over a distance of 1,500 feet for such a train to be stopped

B whereas previously 5 hand brakes operating over a distance of 1,500 feet had been required to stop such a train

C but before stopping the train required 5 hand brakers operating over a distance of 1,500 feet

D but previously they required 5 hand brakers over a distance of 1,500 feet stopping the train

E but before stopping such a train required 5 hand brakers over a distance of 1,500 feet

There seems to be some problem with the question, probably in the transcription. The use of the word 'hand brakers' is jarring. There is no such word as 'hand brakers.' It should be only handbrakes. Notwithstanding that,

If in the hall, if you find it too hard to decipher the difference between 'whereas' and 'but,' try this shorter method

A, and D are merely gone since there is no referent to the plural 'they.'

C and E are gone as they are using simple past tense for the earlier event that happened before 1887. Of course, we may console ourselves that the word 'before' has been used to mark the timeline, but in that case, the question remains as to why a past perfect ' had been developed' used even with a following timeline of the year 1887.

Therefore, B is crisp and clear.

D

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The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

Updated on: 06 Nov 2021, 04:53

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"such a train" is correct. "the train" is incorrect because there are 2 similar trains, but not 1 train.

"the brakes operating over ..." is correct in choice b. in choice e, " required brakes over ..." is meaningless. "brakes over a distance" is meaningless.

"they" is incorrect.

so, we dont have to use knowledge of past perfect to go to OA.

past perfect is use to show
1, an action finished before a past action
2, an action happen before a past action and we dont know the first action finished before the second action or not.

so, past perfect in choice b is correct.

Originally posted by thangvietnam on 29 Jan 2019, 08:08.
Last edited by thangvietnam on 06 Nov 2021, 04:53, edited 1 time in total.

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

02 Oct 2019, 00:17

egmat VeritasKarishma GMATNinja please help with option C and E. since we have word 'before' usage of past perfect is optional. Also, the first perfect 'had been developed' is an earlier event then what is later event in the sentence.

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

03 Oct 2019, 03:55

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kj1993 wrote:

egmat VeritasKarishma GMATNinja please help with option C and E. since we have word 'before' usage of past perfect is optional. Also, the first perfect 'had been developed' is an earlier event then what is later event in the sentence.

The W... had been developed to such an extent by 1887 that a train of 50 cars could be stopped in the space of 171 feet, whereas previously 5 hand brakes operating over a distance of 1,500 feet had been required to stop such a train.

Notice the contrast in the sentence - by 1887, 50 cars could be stopped in 171 feet, whereas previously 5 hand brakes over 1500 feet were required

... but before stopping the train required 5 hand brakers operating over a distance of 1,500 feet
It is unclear what role before plays here. It sounds like the train required 5 hand brakes before stopping and that begs to ask the question - what about after stopping?
What we want to say is that previously, the train required 5 hand brakes to stop.

Also use of whereas is better.

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

29 Jul 2020, 10:53

VeritasKarishma wrote:

kj1993 wrote:

egmat VeritasKarishma GMATNinja please help with option C and E. since we have word 'before' usage of past perfect is optional. Also, the first perfect 'had been developed' is an earlier event then what is later event in the sentence.

The W... had been developed to such an extent by 1887 that a train of 50 cars could be stopped in the space of 171 feet, whereas previously 5 hand brakes operating over a distance of 1,500 feet had been required to stop such a train.

Notice the contrast in the sentence - by 1887, 50 cars could be stopped in 171 feet, whereas previously 5 hand brakes over 1500 feet were required

... but before stopping the train required 5 hand brakers operating over a distance of 1,500 feet
It is unclear what role before plays here. It sounds like the train required 5 hand brakes before stopping and that begs to ask the question - what about after stopping?
What we want to say is that previously, the train required 5 hand brakes to stop.

Also use of whereas is better.

VeritasKarishma So, can I say that "stoping in C and E is a dangling modifier? I mean, who stopped the train? Does that makes sense? Tks!

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

03 Aug 2020, 02:18

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Will2020 wrote:

VeritasKarishma wrote:

kj1993 wrote:

egmat VeritasKarishma GMATNinja please help with option C and E. since we have word 'before' usage of past perfect is optional. Also, the first perfect 'had been developed' is an earlier event then what is later event in the sentence.

The W... had been developed to such an extent by 1887 that a train of 50 cars could be stopped in the space of 171 feet, whereas previously 5 hand brakes operating over a distance of 1,500 feet had been required to stop such a train.

Notice the contrast in the sentence - by 1887, 50 cars could be stopped in 171 feet, whereas previously 5 hand brakes over 1500 feet were required

... but before stopping the train required 5 hand brakers operating over a distance of 1,500 feet
It is unclear what role before plays here. It sounds like the train required 5 hand brakes before stopping and that begs to ask the question - what about after stopping?
What we want to say is that previously, the train required 5 hand brakes to stop.

Also use of whereas is better.

VeritasKarishma So, can I say that "stoping in C and E is a dangling modifier? I mean, who stopped the train? Does that makes sense? Tks!

A subject certainly seems to be missing when you say "before stopping the train required 5 ..." since it seems that "before" acts as a preposition. The verb "required" seems to have no subject.
It seems to be going in this direction: Before stopping the train, you require to check...
which is obviously incorrect. We need before to show previous time.

Hence, "previously" which is clearly an adverb, is much better.

P

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Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

05 Nov 2021, 04:33

Hi Experts

GMATNinja VeritasKarishma EducationAisle ChrisLele mikemcgarry AjiteshArun egmat sayantanc2k RonPurewal DmitryFarber MagooshExpert avigutman EMPOWERgmatVerbal MartyTargetTestPrep ExpertsGlobal5 IanStewart
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Can you please explain me the usage of "Been" in had Been. Like why do we use it, what's the purpose and is it a verb , preposition or any other thing?

gmatclubot

Re: The westinghouse air brake, first demonstrated successfully in 1868 [#permalink]

05 Nov 2021, 04:33

GMAT Sentence Correction (EA only) Questions

The westinghouse air brake, first demonstrated successfully in 1868