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

[MBA Applicant 2007/8]

Ozone, a special form of oxygen that screens out harmful UV 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 chloroflorocarbons 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


My choice is B but the correct choice is D. Please explain.

I chose B because the NON underlined portion is in present tense as in "reaches high con..." although the second half of the sentence does have the past tense "realized".

[dbernst]

The verb tense in the underlined part of the sentence must be compared with what is taking place now. As the sentence states we have realized that emissions of industrial chloroflorocarbons deplete the ozone layer (present perfect), we need the past perfect had appeared to indicate a time period prior to the present. Additionally, "immune from" means free of exempt from (eg. immune from prosecution), whereas "immune to" means not susceptible (eg. immune to chicken pox). In this case, the ozone layer was considered not susceptible to human influence. Thus, "immune to" is idiomatically correct.

-dan

Ozone, a special form of oxygen that screens out harmful UV 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 chloroflorocarbons 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

[Aaorn]

Ozone, a special form of oxygen that screens out harmful UV 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 chloroflorocarbons 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

Still want to know why E is not correct. Thanks !

[JonathanSchneider]

E is too wordy. "appeared immune" is just fine on its own. Notice that we have "it appeared immune." The "it" here refers to the ozone. Thus, to say: "it appeared that it was immune" would be unnecessary.

[kvitkod]

Could smb explain why we cannot use present perfect rather than past perfect to indicate a time period prior the present (like in a, b, c)? Particularly - why C is wrong?

many thanks!

The verb tense in the underlined part of the sentence must be compared with what is taking place now. As the sentence states we have realized that emissions of industrial chloroflorocarbons deplete the ozone layer (present perfect), we need the past perfect had appeared to indicate a time period prior to the present.

[saptadeepc]

Could smb explain why we cannot use present perfect rather than past perfect to indicate a time period prior the present (like in a, b, c)? Particularly - why C is wrong?

many thanks!

The verb tense in the underlined part of the sentence must be compared with what is taking place now. As the sentence states we have realized that emissions of industrial chloroflorocarbons deplete the ozone layer (present perfect), we need the past perfect had appeared to indicate a time period prior to the present.

Consider an example.

I have received a high score in GMAT.

You would not say "I have prepared hard for it"

rather you would say

"I had prepared hard for it."

Even though "have VERBed" shows something whose effect is in present, it is something that "has" already happened. And if we want to point some event that happened before, we need to use "had"

[RonPurewal]

Consider an example.

I have received a high score in GMAT.

You would not say "I have prepared hard for it"

rather you would say

"I had prepared hard for it."

no; if you were to make this statement by itself, you would just say "i prepared thoroughly" (not had prepared).
you might use this tense if the act of receiving a high score were mentioned explicitly -- "i received a high score because i had prepared thoroughly" -- but not otherwise.

[yuanhongzhi0830]

Consider an example.

I have received a high score in GMAT.

You would not say "I have prepared hard for it"

rather you would say

"I had prepared hard for it."

no; if you were to make this statement by itself, you would just say "i prepared thoroughly" (not had prepared).
you might use this tense if the act of receiving a high score were mentioned explicitly -- "i received a high score because i had prepared thoroughly" -- but not otherwise.

Hi Ron, I am a little confused here
Now that "I have received a high score in GMAT because I had prepared hard for it" is wrong, then why "It had long appeared immune to XXX, though we have now realized XXX" is right?
Is it because it is a "relatively" good answer (cuz we dont see a past tense here)

[jlucero]

Know your tenses:

Have/has = present perfect (started in the past and continues until now)

Had = past perfect (happened before another event in the past)

1. You need a past tense in order to use the past perfect (I had studied for three years before I took my GMAT).

2. The usage of past and present perfect tenses could work, but again, you need a simple past to say when something started in the past (I had studied for three years before I took my GMAT, but since then I have not wanted to study).

3. The biggest error in the sentence (I have received a high score in GMAT because I had prepared hard for it" is wrong) is meaning: receiving a high score is a one time event (past) not a continuing event (present perfect).

[TooLong150]

Know your tenses:

Have/has = present perfect (started in the past and continues until now)

Had = past perfect (happened before another event in the past)

1. You need a past tense in order to use the past perfect (I had studied for three years before I took my GMAT).

2. The usage of past and present perfect tenses could work, but again, you need a simple past to say when something started in the past (I had studied for three years before I took my GMAT, but since then I have not wanted to study).

3. The biggest error in the sentence (I have received a high score in GMAT because I had prepared hard for it" is wrong) is meaning: receiving a high score is a one time event (past) not a continuing event (present perfect).

Experts, if we need simple past tense in order to use the past perfect, how is the use of the past perfect justified in D? Is this a special case of the past perfect?

[RonPurewal]

You don't need an actual past-tense verb. You just need a clear indicator of a definite point in the past——the point that serves as the point of view for "had ___ed".

In this sentence, it's clear that, at present, ozone does not appear "immune to xxxxx".
So, the context is this:
• At some point in the past, people thought that ozone was immune to xxxx. For some time up to that point, it had appeared that way.
• Now, we know this isn't true anymore.

Same thing with "By 1990, all of Cynthia's granddaughters had gotten married". 1990 isn't a past-tense verb, but it's plenty good enough as a past reference point for "had ___ed".

[Crisc419]

but, here we do not have a past time or past tense to indicate that we should or can use "had+v-ed".

could anyone clarify?

Thanks.

[RonPurewal]

the past time is implied in the context -- it's whenever we made the discovery that human activities can affect the ozone layer.

[RonPurewal]

also—
as always, when there's a SUBTLE difference in tenses, you DON'T NEED that difference to solve the problem -- there will always be other ways.

in the case of this problem:

•  "immune from..." and "...as being..." are unidiomatic

• the tenses in A and B don't make sense -- both "to have been..." and "was..." imply a timeframe PRIOR to "has long appeared..."
(in context, the timeframe needs to be the SAME as that of "has/had long appeared...")

[Crisc419]

also—
as always, when there's a SUBTLE difference in tenses, you DON'T NEED that difference to solve the problem -- there will always be other ways.

in the case of this problem:

•  "immune from..." and "...as being..." are unidiomatic

• the tenses in A and B don't make sense -- both "to have been..." and "was..." imply a timeframe PRIOR to "has long appeared..."
(in context, the timeframe needs to be the SAME as that of "has/had long appeared...")

totally understand, thank you, Big Ron.