Some epidemiologists believe that the Ebola virus originally has

I had selected A instead of D because though D has similar construction and I understand the point of present perfect not required here as the non-underlined section mentions "originally", thus negating the use of present perfect and past tense, emerged is a good choice.

However in the option D, emerged comes after originally and thereafter a comma. I got confused on whether this is a verbed modifier. I still need this clarification

Actually right option is using the placement of emerged right after originally because it shows that initially how one thing emerged. In fact present perfect is wrong because something has happened in the past.

ruchi857, I don't see a comma in any of the choices. "Emerged" is the verb for the subject "Ebola virus." It's not a modifier.

look at choice A and C. why present perfect is wrong here.
2 cases for present perfect
first, it is used to show an action from the past until presetn. this is not the case in here.

second , it is used to show a finished action in an unfinished time frame. it sound good that it is the case in here. but no.

the finished action must be happen in the unfinished time frame. this action must go with an unfinished time words such as this month or this year. I have learn english this month. the implication is that in the period of this month (until present), I have learned english.

so, second case is not fit inhere. "emerging" dose not happen in an unfinished time. there is no unfinished time in this context of "believed" .

so, has emerged is incorrect inhere.

this analysis require proper understanding of present perfect.

A is the correct option.Why D kindly please explain?

Posted from my mobile device

Official Explanation:

Since the underlined portion of the sentence contains a verb, check whether the verb is consistent with the rest of the sentence. The present perfect tense verb has emerged suggests that the action is ongoing, even though the sentence indicates that the action occurred and ended in the past, which makes the simple past the correct tense. This is a verb tense error, so eliminate choice A and look for any obvious repeaters. There are no obvious repeaters, so evaluate the remaining answer choices individually, looking for reasons to eliminate each.

Choice B incorrectly uses the past progressive tense was emerging, even though the sentence requires the simple past tense, so eliminate choice B. Choice C corrects the verb tense error by using the simple past tense form emerged, but creates a modifier error by placing the phrase, where there is more frequent contact, after host rather than after sparsely populated region of Africa, thereby changing the meaning of the sentence. Eliminate choice C. Choice D corrects the verb tense error by using the simple past tense form emerged, and introduces no new errors, so keep choice D. Choice E incorrectly uses the past progressive tense was emerging, even though the sentence requires the simple past tense form emerged, so eliminate choice E.

Choice A: No. This choice incorrectly uses the present perfect tense verb has emerged in a sentence that requires the simple past tense emerged. Verb tense.

Choice B: No. This choice incorrectly uses the past progressive tense was emerging in a sentence that requires the simple past tense emerged. Verb tense.

Choice C: No. The phrase, where there is more frequent contact, incorrectly modifies host rather than sparsely populated region of Africa. Misplaced modifier.

Choice D: Correct

Choice E: No. This choice incorrectly uses the past progressive tense was emerging in a sentence that requires the simple past tense emerged. Verb tense.

The correct answer is choice D.

Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.