Mathematical applications used to create behavior models in life sciences such as biology and genomics, a relatively recent application that started in earnest in the early 1980’s, has contributed significantly to the development of new medications that are improving the length and quality of life for people who were once thought to have untreatable terminal illnesses.

C: Mathematical applications used to create behavior models in life sciences such as biology and genomics, a relatively recent application that started in earnest in the early 1980’s, have contributed significantly to the development of new medications that are improving the length and quality of life for people who were once thought to have untreatable terminal illnesses.

D: Mathematical applications used to create behavior models in life sciences such as biology and genomics, a relatively recent application that started in earnest in the early 1980’s, contributed significantly to the development of new medications that improve the length and quality of life for people who were once thought to have untreatable terminal illnesses.

The explanation of why D is incorrect says, "In this answer choice, the modifier "a relatively recent application that started in earnest in the early 1980’s" is incorrectly situated such that it seemingly applies to "models" or "genomics" as opposed to the applications. "

Question 1) please explain the explanation for D. The modifier is placed the same way as it is in the correct answer C, no?
Question 2) what about the verb tense?

i still do not understand why D is any less correct than is C.
Thank you.

I'm looking into this one. Will get back to you...

OK, so I agree with you that there is a discrepancy here between our explanation and the given choices. You are right to say that the modifier is the same in both C and D. And while the present perfect is probably preferred here (given the word "recent" earlier in the sentence), that does not make D incorrect. So, we'll have to review this one. Thanks for the heads up!

Any updates on this ?

As Jon mentions, I'd prefer the present perfect verb tense

Also in C, we have
Math apps used to X, contributed to Y that <improve >

Shouldn't we have if C were correct ?
Math apps used to X, contributed to Y that <improved>

not if you're talking about drugs that improve patients' quality of life, such as the ones in this problem.

if you use the past tense, then it implies that whatever you're talking about is actually IN THE PAST. i.e., it's not actually happening anymore; whatever effect is under discussion is no longer occurring.

in this sentence, the most reasonable interpretation is that the drugs STILL contribute to quality of life, even though the research in the question has already been completed. thus the different tenses.

here's another example:
in the 16th century, physicians discovered that human blood circulates through the body.
this is correct.
you don't want to say "circulated", since, of course, blood still circulates in the present world.

Guys,

in this ques-- "a relatively recent application that started in earnest in the early 1980’s"

the bold lines shows that application started in early 1980....so only start time is given....so we use present perfect to indicate that that application still going on..

good analysis!

_________________
Tim Sanders
Manhattan GMAT Instructor