While global temperatures have risen sharply

[Mo2men]

While global temperatures have risen sharply over the last century, they have only recently eclipsed the Medieval period, during which scientists theorize that a series of volcanic eruptions sent the earth into a period of historic warmth.

A. they have only recently eclipsed the Medieval period, during which scientists theorize that a
B. they have only recently eclipsed those of the Medieval period, during which scientists theorize that a
C. it has only recently eclipsed the Medieval period, during which, scientists theorize, a
D. it has only recently eclipsed that of the Medieval period, during which scientists theorize a
E. they have only recently eclipsed those of the Medieval period, during which, scientists theorize, a

Source: Veritas

[Ali Tariq]

Hello Mo2men,

A) they have only recently eclipsed the Medieval period, during which scientists theorize that a
-->illogical comparison-->temperatures eclipsed period.


during Medieval period, scientists theorize that a series of volcanic eruptions sent the earth into a period of historic warmth
-->illogical meaning/ contrary to the fact meaning since scientists didn't theorize during Medieval period; instead a series of volcanic eruptions sent the earth into a period of historic warmth during Medieval period.

-->Further,
during Medieval period, scientists theorize that a series of volcanic eruptions sent the earth into a period of historic warmth

during Medieval period is an inital modifier modifying verb theorize
Tense conflict: Simple present tense for an event(theorize) that occured in past.

B) they have only recently eclipsed the Medieval period, during Medieval period, scientists theorize that a series of volcanic eruptions sent the earth into a period of historic warmth.

-->comparison is fine, unlike that in A.
-->meaning/logic and tense errors, like those in A



C) it has only recently eclipsed the Medieval period, during which, scientists theorize, a
-->pronoun error: it cannot refer to temperatures.
-->illogical comparison, as is the case in A.

D) it has only recently eclipsed that of the Medieval period, during which scientists theorize a
-->pronoun error.
-->same logic/meaning and tense errors as were in A and B.

ans is E.

E. they have only recently eclipsed those of the Medieval period, during which, scientists theorize, a

-->Scientists theorize is a non essential modifier and thus we can get rid of it without changing intended meaning.

-->No tense conflict as was the case in A ( as well as in B and D ):
during Medieval period, a series of volcanic eruptions sent the earth into a period of historic warmth.

initial modifier during Medieval period modifying sent, which is not in simple present tense, unlike tense in A , which is simple present tense.

[GMATGuruNY]

Generally, while serves to introduce a contrasting event that happens AT THE SAME TIME as the main clause.

OA: While global temperatures have risen sharply over the last century, they have only recently eclipsed those of the Medieval period.
Here, while serves to contrast an event that happened OVER THE LAST CENTURY with an event that happened ONLY RECENTLY.
This usage of while seems illogical.

Another issue:
In the OA, they and those both serve to refer to global temperatures.
On the GMAT, different pronouns should not have the same referent.

I would ignore this SC.

[Mo2men]

Another issue:
In the OA, they and those both serve to refer to global temperatures.
On the GMAT, different pronouns should not have the same referent.

I would ignore this SC.

Hi Mitch,

I know the following rule:

successive forms of same pronoun must have same referent.

If we apply the same rule above:

'they' & 'their' refers to 'temperature'. So there is no problem.

Why do you consider it wrong?

Thanks

[GMATGuruNY]

Third-person pronouns: he, she, it, they, him, her, it, them, his, her, its, their.
Demonstrative pronouns: this, that, these, those.

Another issue:
In the OA, they and those both serve to refer to global temperatures.
On the GMAT, different pronouns should not have the same referent.

I would ignore this SC.

Hi Mitch,

I know the following rule:

successive forms of same pronoun must have same referent.

If we apply the same rule above:

'they' & 'their' refers to 'temperature'. So there is no problem.

Why do you consider it wrong?

their is not included in the OA.
The two pronouns included in the OA are they and those.
they (third-person pronoun) and those (demonstrative pronoun) are not forms of the same pronoun.