In some species of cricket, the number of chirps per minute used by th

Very safe! We can write "Tim likes burritos" or "Tim must love enchiladas."

Nice work!

Hi experts GMATNinja AndrewN IanStewart

I could see why (E) is incorrect, but I have one doubt for the correct answer (D).

I have been told that in written English, we use "and" to connect two independent clauses only when there is no logical relationship between the two clauses. In other words, the two clauses are independent in terms of meaning.

But I think that is not the case here--the first clause that the number of chirps rises and falls in accordance with the temperature is the reason/supporter for the claim the number of chips can/has the ability/is able to serve as a thermometer. Hence, should not (D) say ".... with the surrounding temperature, and thus it can in fact serve..."?

I am not saying that the option (D) should not be the correct option, but wondering how much we can rely on the concept that "and" cannot connect clauses with logical relationship? After learning this concept, I have used it to solve some SC questions successfully. Now, I am confused how solid this rule is.

Or, would you advise me to consider this question a special case? Is (D) the winner because it is superior to (E) despite the "and" issue?

Thank you very much!

We do use "and" in that way, but we don't only use "and" that way. We often use "and" when describing the consequence of one event, for example:

"Anton spelled the company's name incorrectly on his job application, and this led the company to hire a different candidate."

and I'm sure there are dozens of other situations where we use "and" to connect clauses that are logically related. The important question is whether the words correctly convey the logical relationship the sentence intends to convey. If "and" does that effectively, then "and" is a good word to use. If "and" does not indicate the logical relationship successfully, then a different word should be used.

Hello, GraceSCKao. I have little to add to the response you have already received. Even so, I will respond in-line below to a few issues you have raised.


I have no idea who makes up these so-called rules. I would be curious to know what such a teacher would have to say about sentences in which the second independent clause begins with and yet.


Well done on not shutting down your mind to other possibilities. The sentence could be written with thus, but obviously, the extra word is not required. I am curious about these other SC questions you mentioned. My guess is that they each present other issues that allow you to build a stronger case than simply relying on a certain relationship between clauses joined by and.

Thank you for thinking to ask.

- Andrew

Thank you IanStewart and AndrewN for your responses and explanations!

AndrewN, I am always happy to receive your response, and appreciate your time and thoughts. Thank you for willing to discuss this topic. I decide to write a follow-up post, since I feel that I might have misled you about the concept I mentioned in my first post.

The advice I have been given is: If the two independent clauses have no logical relationship, we can use the conjunction "and" alone to connect the two clauses. But if the two clauses have some relationship, we either use another suitable conjunction (such as "so") or we add another suitable word following "and" (such as "and thus") to convey the relationship.

Hence, according to this concept, it is viable to use "and yet," but it is not viable to use "and" merely to connect two clauses whose meanings are in a contrast. An example would be "To my untutored eye, it just looks like a load of random brush strokes and yet it is a very valuable painting." I am sorry if I made you misunderstand in my previous post.

Since GMAT club experts often say "Do not invent rules." and I also feel that there are only few ironclad rules that we count on, such as SV agreement, no fragment/run-on, parallelism, "more...than," and "as...as," when I knew this concept/rule, I was not only surprised but also a bit suspicious--I noticed that this concept is seldom mentioned at this forum, but sometimes appears at other forums.

But, I began to trust this concept to some degree after I found that some official questions can be analyzed with this concept. I will list a few below, with only the options relevant to this topic involved. But I agree with you that some incorrect options contain other issues than the so-called "and" issue. It is just that I could solve them more quickly by using the "and" issue. It would be great if you could share some thoughts when you have time (if you are interested in continuing this discussion.)


->My process with the "and" issue:
The two clauses are not independent because the first explains the reason why tasting the substance can help flies distinguish species, so it is incorrect to use "and" alone to connect the clauses. Eliminate (A) and (B). Is "assist..to do sth" a correct idiom? No. Eliminate (D).

->My process without the issue:
In (A), "this" is unclear but maybe not a definite error. But I can eliminate (A) and (D) for the use of "assist..to do sth." In (B), "Assist..in doing sth" seems correct. The use of "when" is weird, but is it a definite error? Not sure how to eliminate (B). But (E) seems better so let me pick (E).

By the way, I think that this question resembles the cricket chirp question in that the first part explains the second part in both sentences. But interestingly, the hydrocarbon question's correct answer uses the comma-ing structure, while the cricket question's uses two independent clauses.

"In some species of cricket, the number of chirps per minute used by the male to attract females rises and falls in accordance with the surrounding temperature, and it can in fact serve as an approximate thermometer."

"Hydrocarbons, with which fruit flies perfume themselves in species-specific blends, are known to be important in courtship, apparently assisting flies that taste the hydrocarbons on prospective mates in distinguishing their own species from others."

Another official question:

->My process with the "and" issue:
Energy production is the intention of the heat mining, so it is incorrect to use "and" in (A) or (B). Elimate (A) and (B).

->My process without the issue:
(A) has parallelism issue in "for efficient generation of electricity and heating." Eliminate (A).
In (B), "for electricity to be generated efficiently and to heat" seems strange, since it is in passive and active tone at the same time. But is it a definite error? Not sure. Do we say "the power heats the factories" or "the power is used to heat the factories"? No idea. I cannot eliminate (B), but (D) does not leave so many questions in my mind, so pick (D).

The last example:

This one is less concerning, because (A), (B), (C) and (D) all contain parallelism issues with the use of "either...or." But it has been pointed out that GMAC desgins the correct option, (E), this way because "date" and "were fashioned" are separate/ independent ideas--so it is correct to use "and" only to connect the two parts.

Overall, I think that the "and" concept is helpful sometimes, but after practicing the cricket chirp question, I feel that like many other SC concepts, this one can only be used flexibly.

Just as I suspected, GraceSCKao, there are far worse offenses in every question you brought up besides this apparently non-functional and. In the fly question, the demonstrative this is awful, not at all clear, and what are we to make of those of at the end of answer choice (B)? Distinguishing their own species from [the species (plural)] of others? If I were to write a similar line about distinguishing my (singular) toy from a pile of toys, would I say distinguish my toy from a pile of the toys of others? No, I would focus on what needs to be distinguished: one toy from among many, one toy from other toys, or one toy from others. I will cut you a little slack, since species is one of those words that appears identical in singular and plural forms. Still, you should know how tightly the GMAT™ likes to keep comparisons, and the jump from one species to multiple species puts the two elements on uneven footing.

In the energy question, and holds the two noun phrases in parallel: succeeded in mining and producing... Such a construct does away with the cause-and-effect relationship expressed by mining... to produce. Answer choice (A) has a glaring lack of parallelism at the end, as you pointed out. You did the right thing to compare one answer choice you doubted in (B) and another one you did not. So, while I would say that and is the biggest problem with (B), it is not for the reason you were taught.

Finally, in the Kushan empire question, that and simply joins two parallel elements: date from and were fashioned from. The second part is not an independent clause, just an equally valid continuation of the main clause: Many... deities... were fashioned either from X or from Y. This usage is quite common in SC questions and is not the same as what you were inquiring about initially.

Thank you for more clearly outlining what you were taught. I would advise you to focus on other issues, for obvious reasons. (This question is no exception to a general rule on and.)

I appreciate your following up.

- Andrew

Thank you AndrewN for your responses and thoughts on the questions!

Yesterday I checked other official questions used in the tutoring sessions of the "and" concept, and found that most, or almost all, incorrect options whose use of "and" is suspicious contain other errors, many of them more glaring than the "and" issue. I am relieved after finding out this--I think I could address other more-concrete issues first. It is said that each incorrect SC option has at least two mistakes, but I am not sure whether the use of "and" is the other mistake.

Personally speaking, I still think the "and" concept has its value--it has a point that if two units have a strong logical relation, using "and" solely to connect them would not be enough. But, I also think that it is not an absolute concept, since this cricket chirp question and another starfish question have shown that the use of "and" could be more flexible.

"In some species of cricket, the number of chirps per minute used by the male to attract females rises and falls in accordance with the surrounding temperature, and it can in fact serve as an approximate thermometer."



Starfish, with anywhere from five to eight arms, have a strong regenerative ability, and if one arm is lost it is quickly replaced, with the animal sometimes overcompensating and growing an extra one or two.

I personally think that the use of "and" is fine, but if someone argues that "so" or "therefore" could be used to replace "and", I do not disagree. I would not feel awkward if the correct option used "so" instead of "and."

Overall, I've decided to consider this concept supplementary. It would not be my first elimination point. If there is a strong cause-effect relationship or purpose relationship between two elements/clauses/verbs, I might still frown on the use of "and" and check whether other options convey the meaning/relationship more clearly.



Thank you AndrewN for your explanations on these questions. (Strictly speaking, only one of them uses "and" solely to connect two independent clauses. I found this when I reviewed my post, but decided not to remove the other two questions since I thought they could be discusses together. The "and" concept I learned applies to the connection of two clauses or of two verbs.)

I would like to share some thoughts about the fruit flies question. I did not use "those" to eliminate options--I genuinely thought that "those" refers to "species" and the non-underlined "others" refers to "other flies," so the option (B) read to me "assists flies...in distinguishing their own species (plural) from species (plural) of other flies." It is not economical or concise, but it is not redundant. My idea is that redundancy is a definite error, but not being concise is not. (Though, many incorrect options are not concise.) So I could not eliminate (B) by examining the option solely, although the use of "this" and "when" is suspicious. I eliminated it after comparing it and option (E).

Hydrocarbons, with which fruit flies perfume themselves in species-specific blends, are known to be important in courtship,

(B) and apparently this assists flies when they taste the hydrocarbons on prospective mates in distinguishing their own species from those of [others.]
(E) apparently assisting flies that taste the hydrocarbons on prospective mates in distinguishing their own species from [others.]

I think you have a great point that GMAT likes to keep comparisons tightly. The fact that some words are identical in singular form and plural form does help the test designers increase the difficulty, as do the collective nouns.

Thank you for your insights, also for willing to spend your time discussing this topic with me.
Really appreciate your thoughts and responses.

I could narrow down to the choices D and E, and ended up picking the right choice D. But, I wish to know from experts whether I was smart enough with my logic or I was blatantly lucky.

Both the options, D & E, are error-free grammatically (at least unlike the other options which are eliminated). Now, we know that there is surely some meaning difference between the two (the last two grammatical choices are usually about the meaning, isn't it?). Without draining much energy, I could see that the choice D is in coherence with the given sentence in terms of meaning as they both, option D and the given sentence, use "can" at the end, whereas choice E uses some other form, a verb'ing' modifier that modifies a preceding action (but is defintely not talking about "can" or potential, and is rather implying some causal-effect relationship with the preceding clause). Whatever is the intended meaning, I don't care. But, what I DO care about is that the meaning in the correct choice should be in-line with that in the given sentence. (we need to ensure that we do not miss out the intended meaning of the author, and the author conveys his meaning to us via the given sentence only, right?) Option D seems to follow the intended meaning of the given official sentence, but I am not really sure "what" meaning it is conveying as long as the meaning is SAME! (Honestly, I have seem this works in most official questions. But, I use it only when I am lost in the last 2-3 gramatical options.)

Hello Pankaj0901,

We hope this finds you well.

To answer your query, your reasoning is broadly correct.

Kudos.

To provide just a bit more clarity, through the use of "can", the original sentence conveys a sense of possibility, while the construction "possibly serving" seems to imply that the action is practically taking place.

We hope this helps.

All the best!
Experts' Global Team

GMATNinja KarishmaB
Can you please help me with concepts of Subject verb agreement for this question?
Is their any rule to decide whether to use singular or plural with "The number of" ?

I am confused with SV agreement in the question below. It follows a different rule.

The tourism commission has conducted surveys of hotels in the most popular resorts, with the ultimate goal of reducing the guests who end up expressing overall dissatisfaction with the service in the hotels.

(A) with the ultimate goal of reducing the guests who end up expressing overall dissatisfaction with the service in the hotels

(B) with the goal to ultimately reduce the number of guests who end up expressing overall dissatisfaction with the hotels’ service

(C) ultimately with the goal to reduce expressions of overall dissatisfaction by the guests with the hotel service

(D) in an ultimate attempt to reduce the number of guests that ends up expressing overall dissatisfaction with the hotels’ service

(E) with the ultimate goal of reducing the number of guests who express overall dissatisfaction with the hotels’ service

Hello adyg14,

We hope this finds you well.

To answer your query, the phrase "number of" is always followed by a plural noun.

As you can see, this question uses the phrase "the number of chirps", and the sentence you have provided uses the phrase "the number of guests"; both "chirps" and "guests" are plural nouns.

We hope this helps.
All the best!
Experts' Global Team

'The number of' is followed by a singular noun. We are talking about the actual number.
The number of birds in the city is decreasing.
Singular 'is' refers to 'number.'

'A number of' means 'many.'
A number of birds make their nests in these trees.
means 'many birds make their nests in these trees'

Now look at this:

The number of birds that make their nests in these trees is decreasing.

The relative clause 'that make their nests in these trees' refers to 'birds' which is plural. Hence we use 'make' (plural).
'that' stands for only 'birds.' We are modifying only birds, not the number.

The verb 'is' agrees with the singular 'number' since it is the number that is decreasing.

This is exactly what is happening in option (E) too.
'who' stands for 'guests.'

There is always conflict between concepts i have learnt. In this question i conflicted with concept that do not start a new sentence if work is done in a single sentence so i crossed D option. But E has also error of meaning that in fact and possibly can't make much sense. Expert I would really appreciate if you know how to solve this conflicting type questions?

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So you're down to two choices. One of those choices makes perfect sense, but violates some vague and subjective grammar "rule" that you've picked up somewhere ("do not start a new sentence if work is done in a single sentence"). The other has a meaning issue and doesn't make any sense ("E has also error of meaning that in fact and possibly can't make much sense"). Which of those sounds more important?

Borrowing from an earlier post: there are painfully few absolute rules that ALWAYS apply on GMAT SC -- other than subject-verb agreement, it's hard to think of many. The more important question: "is the structure in this particular answer choice the best and clearest way to express a reasonable meaning for the sentence?"

Unfortunately, many students try to turn GMAT SC into a mechanical test, desperately creating a never-ending list of "rules" that can be applied to future questions. But GMAT SC doesn't work that way. Yes, certain grammar rules are important and valuable. But once you've eliminated choices that have DEFINITE errors, you have to think really hard about the differences in meaning among the remaining choices and determine which choice is the best. That part is difficult and unsatisfying, and memorizing an ever-growing list of questionable grammar "rules" won't help much.

For more on that, check out this post: https://gmatclub.com/forum/a-recent-pol ... l#p2421717. And for more on how to set your priorities in general on SC, check out this video.

I hope that helps a bit!

Hey egmat ,
in option E, if "fact possibly' was not there in 'in fact possibly serving', can 'serving' serve as modifier to verb 'rise and fall'?