Ozone, a special form of oxygen that screens out harmful ultraviolet

Dear Friends,

Here is a detailed explanation to this question-

Concepts tested here: Tenses + Pronouns + Idioms + Awkwardness/Redundancy

• A noun and its derivatives can only have one referent in a particular sentence.
• “immune to” is the idiomatic construction.
• The past perfect tense (marked by the use of helping verb "had") is used when a sentence contains two actions in the past; the helping verb "had" is used with the action in the "greater past".
• The present perfect tense (marked by the use of the helping verb “has/have”) is used to describe events that concluded in the past but continue to affect the present.
• “being” is only to be used when it is part of a noun phrase or represents the passive continuous verb tense; the use of passive continuous must be justified in the context.

A: This answer choice incorrectly uses the present perfect tense verb “has…appeared” to refer to the earlier of two actions that concluded in the past – ozone long appearing immune to human influence and us realizing that emissions of industrial chlorofluorocarbons deplete the ozone layer; remember, the past perfect tense (marked by the use of helping verb "had") is used when a sentence contains two actions in the past; the helping verb "had" is used with the action in the "greater past", and the present perfect tense (marked by the use of the helping verb “has/have”) is used to describe events that concluded in the past but continue to affect the present. Further, Option A incorrectly uses the pronoun “it” both as a placeholder pronoun and to refer to the noun “Ozone”; remember, a noun and its derivatives can only have one referent in a particular sentence. Additionally, Option A incorrectly uses the unidiomatic construction “immune from”; please remember, “immune to” is the idiomatic construction. Besides, Option A uses the needlessly wordy phrase “appeared that it was immune”, leading to awkwardness and redundancy.

B: This answer choice incorrectly uses the present perfect tense verb “has…appeared” to refer to the earlier of two actions that concluded in the past – ozone long appearing immune to human influence and us realizing that emissions of industrial chlorofluorocarbons deplete the ozone layer; remember, the past perfect tense (marked by the use of helping verb "had") is used when a sentence contains two actions in the past; the helping verb "had" is used with the action in the "greater past", and the present perfect tense (marked by the use of the helping verb “has/have”) is used to describe events that concluded in the past but continue to affect the present. Further, Option B incorrectly uses the unidiomatic construction “immune from”; please remember, “immune to” is the idiomatic construction. Additionally, Option B uses the needlessly wordy phrase “appeared to have been immune”, leading to awkwardness and redundancy.

C: This answer choice incorrectly uses the present perfect tense verb “has…appeared” to refer to the earlier of two actions that concluded in the past – ozone long appearing immune to human influence and us realizing that emissions of industrial chlorofluorocarbons deplete the ozone layer; remember, the past perfect tense (marked by the use of helping verb "had") is used when a sentence contains two actions in the past; the helping verb "had" is used with the action in the "greater past", and the present perfect tense (marked by the use of the helping verb “has/have”) is used to describe events that concluded in the past but continue to affect the present. Further, Option C needlessly uses the word "being", leading to awkwardness and redundancy; remember, “being” is only to be used when it is part of a noun phrase or represents the passive continuous verb tense; the use of passive continuous must be justified in the context.

D: Correct. This answer choice correctly uses the past perfect tense verb “had…appeared” to refer to the earlier of two actions that concluded in the past – ozone long appearing immune to human influence and us realizing that emissions of industrial chlorofluorocarbons deplete the ozone layer. Further, Option D correctly uses the pronoun “it” for only one purpose, as a placeholder pronoun. Additionally, Option D uses the idiomatic construction “immune to”. Besides, Option D is free of any awkwardness or redundancy.

E: This answer choice incorrectly uses the pronoun “it” both as a placeholder pronoun and to refer to the noun “Ozone”; remember, a noun and its derivatives can only have one referent in a particular sentence. Further, Option E uses the needlessly wordy phrase “appeared that it was immune”, leading to awkwardness and redundancy.

Hence, D is the best answer choice.

To understand the concept of "Past Perfect Tense" on GMAT, you may want to watch the following video (~2 minutes):



To understand the concept of "Present Perfect Tense" on GMAT, you may want to watch the following video (~1 minute):



To understand the use of "Being" on GMAT, you may want to watch the following video (~2 minutes):



All the best!
Experts' Global Team

And what I say is -- Snaps and Tarek, you are both correct.

Whenever I and others say that the perfect tense describes an action that happened in the past and "continues up to the present", we are actually oversimplifying somewhat. The perfect tense usually means this, but it can also mean that the action occurred in the past and CREATED A CONDITION which continues to the present AND is relevant. That is what the perfect means in this case: We realized in the past that emissions deplete the ozone layer -- we are NOT still in the process of realizing -- but now we are in a state of KNOWING this, and it matters.

So the event of realizing is a past event. The appearance that the ozone layer was immune to human interference existed BEFORE that past event. For events or conditions that happened before another past event, we use the pluperfect, "had appeared". This reduces the choice to D and E, and E is unnecessarily wordy.

A quick note on the idiom:

"Appear to" is an important idiom here!

Ex. He appears to be a good student.

(There is no structure, "appears as".)

"AS BEING" IS ALWAYS INCORRECT!

Now, if the past is involved in the sentence, then use the perfect infinitive: to + have + V3

Ex. Einstein appears to have been a bad student. (Einstein, now dead, is no longer a student.)

Other idioms like "appear to":
seem to, believed to, estimated to, thought to...

(Idioms are taught in the Small Details lesson at gmaxonline!)

Come on guys check the Oxford Dictionary for idiom usage:

immune /{speaker}Imju:n/ adjective [notusuallybeforenoun]
1 ~ (to sth) that cannot catch or be affected by a particular disease or illness:
Adults are often immune to German measles.
2 ~ (to sth) not affected by sth:
You'll eventually become immune to criticism. * Few men are immune to her charms. * Our business is far from immune to economic conditions.
3 ~ (from sth) protected from sth and therefore able to avoid it
SYNEXEMPT: No one should be immune from prosecution.

IMO, - immune from - is as acceptable as - immune to.-

E. g: Having suffered typhoid a couple of times, Tom is now immune to that disease.

You are immune from contracting sexually transmitted diseases, when you employ safe sex practices (meaning that you are protected from the ill effects of something, when you are immune from them.)

So what decides the use of - to or from - is the context. I would in the given context choose -immune from - rather than - immune to -because the meaning implies that ozone is far placed and hence protected from human influence.

What however baffles me is how we can afford a past perfect here, when the thumb rules state that

1. A past perfect can not remain alone without a simple past.

2. By custom, a past perfect can not be joined with a present tense or a present perfect, without a past tense intervening.

I can not digest choice D and E, unless somebody makes bold to say that the use of past perfect here is an exception under some blah, blah rule.

B on the other hand uses the present perfect tenses for all descriptions - has long appeared to - and -have been immune from - and it goes parallel with the present perfect in non-underlined part - we have now realized -

B for me therefore on my own reckoning.

Very good question. ACE were awkward. I then had to use the "immune to" idiom to pick D over B. I did not understand how to split the answers using the tenses. Can someone explain how the past perfect is used correctly here?

There is some interesting conversations about the perfect tenses in this post . You are starting off correctly with your question by looking at the split of tenses. The GMAT is providing you with a choice between the present and past perfect tenses. Generally speaking, the present perfect tense is used for actions that started in the past but they, or their effects, are still ongoing. The past perfect is used for actions that started in the past but have a definite end. The setup in this problem makes it very clear that the ozone "appearing to be immune" is something that is no longer happening, so you would eliminate the present perfect options.

KW

I was between C and D.

I chose C, even though it sounds a bit awkward. The reason is that "had long appeared immune to" seems to be missing the verb "to be". So, I would have chosen D, if it was phrased as "had long appeared to be immune to".

One question I have is whether C is gramatically incorrect or not (C: has long appeared as being immune to).

No, "appeared as being" is not correct. Being is frequently used incorrectly (but not always!) so if you are between two options and you don't know how to eliminate, you can guess away from 'being'.
KW

Posted from my mobile device

There are two primary issues here:

1) Idioms

"Considered," "Seemed," "appeared" are all words that are often unnecessarily proceeded by a preposition and an adjective. People say, "He seemed to be gigantic," or "She is considered as very industrious," or "they appeared to be insignificant." All of these examples are unnecessarily wordy. In each case the preposition shouldn't be there. "He seemed gigantic," "She is considered very industrious," and "they appeared insignificant" are all preferable to the versions with the prepositions. So when "considered," "seemed," or "appeared" is used to introduce a descriptive word (an adjective), don't use a preposition between the two words.

It's also idiomatic to say "immune to" rather than "immune from")

So D gets the idiom right.

2) Tense

As others have pointed out, D gets the sequence of events clear. The present perfect (which can be thought of as one version of the past tense, despite the name) in "have realized" tells us that the realization happened at some point before the present. We need to make clear that the old perception existed before that more recent realization. Past perfect (had appeared) makes this clear.

Hi Experts,

Could you please let me know what is the issue in option B apart from idiom?

has long appeared to have been immune from

here we are using perfect infinitive and it denotes the prior action then what is mentioned in main clause.

Please clarify this.

Thanks

The use of perfect infinitive is wrong in this case - the fact that it is immune (or not immune) is an universal truth and use of perfect infinitive wrongly implies that it appeared that it was previously immune, but now it may not be.
Another problem with B is the wrong present perfect tense "has appeared". Since the verb "appeared" occured before the verb "realize", past perfect is better.

I'd *heavily* recommend treating this as a Tense/Timeline problem and not an idiom problem. If 100 people see this thread, I'd bet that fewer than 2 ever see "immune to vs. immune from" on an official GMAT, but I'd say 80+ of you will have a decision similar to the verb tense issue here.

Note that after the semicolon you have "we have now realized, though, that..." This means that 1) something has changed (there's a transition here), so 2) the verb tense for what was once thought to be true shouldn't be the same as the verb tense for what has changed. That present perfect "has long appeared" suggests that that appearance is still going on...but immediately past the semicolon we get evidence that that appearance of immunity is over, so we need a verb tense for "long appeared" that shows that the action is over. Only (D) and (E) do that.

Why I'm pretty adamant about seeing this as a tense problem is that it's repeatable...everyone will see verb tense tested on the official GMAT, so the more you've trained yourself to look for signals of timeline (e.g. "hey there's clear evidence that we no longer think this way, so we have to show that "has appeared" is over") the more you're preparing for whichever Tense/Timeline problems the GMAT happens to throw at you that day. Verb tense decision-making is repeatable, whereas if you walk away from this one thinking "immune to > immune from" that's not bad knowledge to have in general, but there's just such a limited probability that you'll get to use it on test day.

And then BARUAH "we have now realized" does put that act of realizing in the past and suggest that anything that happened prior to that realization is further in the past, justifying the past perfect there. Like you I'd probably prefer "it long appeared immune" but since they didn't give us that choice we have to make the best of what we've got and at least "had appeared" clearly puts that appearance in the past before "we have now realized."

Ozone, a special form of oxygen that screens out harmful ultraviolet rays, reaches high concentrations twelve miles above Earth, where it has long appeared that it was immune from human influence; we have now realized, though, that emissions of industrial chlorofluorocarbons deplete the ozone layer.


(A) has long appeared that it was immune from

(B) has long appeared to have been immune from

(C) has long appeared as being immune to

(D) had long appeared immune to

(E) had long appeared that it was immune to


1. I chose answer B though I do understand that ozone "appearing to be immune" is no longer true.

2. Also, I found it difficult to justify answer D as there is no verb in simple past(for the past perfect).
I read a few explanations that state that since "we have now realized ..."(the part that follows semicolon), the realization must have started at some point in the past.
I do agree with the part that "the realization must have started at some point in the past" but there is no action with simple past in the sentence and the above is only our inference.

AjiteshArun , GMATNinja , MagooshExpert , GMATGuruNY , VeritasPrepBrian , MartyTargetTestPrep , DmitryFarber , VeritasKarishma , generis , EducationAisle , other experts - please enlighten

This is slightly confusing because you seem to have given an answer in your own question:).

As you correctly mention: I do agree with the part that "the realization must have started at some point in the past".

So, that realization (that happened at some point in the past) is expressed as present perfect.

By the way, there are many official examples of usage of past perfect, with present perfect. For example:

The success of the program to eradicate smallpox has stimulated experts to pursue something they had not previously considered possible -- better control, if not eradication, of such infections as measles and yaws.

Ozone, a special form of oxygen that screens out harmful ultraviolet rays, reaches high concentrations twelve miles above Earth, where it has long appeared that it was immune from human influence; we have now realized, though, that emissions of industrial chlorofluorocarbons deplete the ozone layer.

(A) has long appeared that it was immune from Clearly, we now know that ozone is not unaffected by humans - usage of present perfect "has appeared", which shows that the action continues into the present, is incorrect. Eliminate.

(B) has long appeared to have been immune from Same error as in (A). Eliminate.

(C) has long appeared as being immune to Same error as in (A) and (B). Eliminate.

(D) had long appeared immune to Correct answer - correct usage of past perfect "had appeared" and no new errors introduced.

(E) had long appeared that it was immune to "that it was" is redundant - it also needs to be in the same timeframe as "had...appeared". Eliminate.

Hope this helps.

Dear GMATNinja - i have had the same understanding and chose B over D. Will u please help to clarify?