The spectacular disintegration of a comet last year in full view of ground- and space-based telescopes provided new insights into how comets form and thus may force a rethinking of the role of comets in the delivery of organic compounds to the evolving earth.

A. The spectacular disintegration of a comet last year in full view of ground- and space-based telescopes provided new insights into how comets form and thus may force

B. The spectacular disintegration of a comet last year in full view of ground- and space-based telescopes, provided new insights into how comets form and thus possibly forcing

C. When a comet's spectacular disintegration occured in full view of ground- and space-based telescopes last year, it provided new insights into how comets form and thus possibly forcing

D. Last year, in full view of ground- and space-based telescopes, a comet's spectacular disintegration provided new insights into how comets form and thus possibly forcing

E. Last year, in full view of ground- and space-based telescopes, the spectacular disintegration of a comet has provided new insights into how comets form and may thus force


Very interesting answer choices. I narrowed it down to 2 (easily), but chose the wrong one. Now I understand why it was wrong, and hope you guys can learn to from the discussion.
_________________

[highlight]Monster collection of Verbal questions (RC, CR, and SC)[/highlight]
massive-collection-of-verbal-questions-sc-rc-and-cr-106195.html#p832142

[highlight]Massive collection of thousands of Data Sufficiency and Problem Solving questions and answers:[/highlight]
1001-ds-questions-file-106193.html#p832133

A seems to looks the best.

B - out because of lackof parallelism
C - this was my other suspect....but the use of "When" should refer to a time period...thought it is "last year," still does not convey the message correctly.
D and E - awkward.

More detailed explanation one-on-one from experts would help.
I don't know if this modifier issue...

I agree with daagh that the use of "and" here necessitates a verb in the first part of the sentence. Notice that there is no verb at all in the non-underlined portion, so you need a verb in the underlined portion. But the underlined portion says "A and thus B"--so A and B need to be parallel, and they must both contain verbs. As daagh says, that knocks off B, C, and D.

I also agree that the meaning shifts in E, but I have a different (grammatical) reason for losing E. There is a verb split between A and E-- "provided" versus "has provided." What might help us distinguish which of these options is incorrect? Both sentences use the phrase "last year," but you cannot use the present perfect tense (has/have + past participle) if you name the specific point in the past when that action happened.

Last year, I ate 10 pizzas. CORRECT
Last year, I have eaten 10 pizzas. INCORRECT

In 1998, I owned twenty pairs of shoes. CORRECT
In 1998, I have owned twenty pairs of shoes. INCORRECT

One thing to be careful of when applying this rule is the word "since"--"since 1998" means...in the period of time between 1998 and leading up to the present," so you *can* use a specific date with "since" and the present perfect.

Since 1998, I have been to Paris four times. CORRECT
In 1998, I went to Paris four times. CORRECT (but different meaning)
In 1988, I have gone to Paris four times. INCORRECT.

E incorrectly uses the present perfect, so A is our answer.
_________________

JP Park | Manhattan GMAT Instructor | Los Angeles

Manhattan GMAT Discount | Manhattan GMAT Reviews