It is possible that Native Americans originally have migrated to the

Present Perfect Tense we used where some work is started in past and just finished some time back. And Past Indefinite Tense we use where some work is completed in some particular time in the past.
In this context Migration happened. So D is the correct choice.

Lets draw the timeline.once existed is a past event. Anything that happen with respect to a past event comes in past tense.
past continuous B and E are just changing the meaning any making no sense at all.A is present tense.
between C and D, you migrate to some place , idiom problem.

(A) have migrated to the Western Hemisphere over a bridge of land that once existed - present tense.
(B) were migrating to the Western Hemisphere over a bridge of land that existed once - past continuous
(C) migrated over a bridge of land to the Western Hemisphere that once existed - you migrate to some place , idiom problem.
(D) migrated to the Western Hemisphere over a bridge of land that once existed - correct
(E) were migrating to the Western Hemisphere over a bridge of land existing once - past continuous

what's wrong with option B?
can anybody please elaborate
GMATNinja

Option B gives us

It is possible that Native Americans originally were migrating to the Western Hemisphere over a bridge of land that existed once between Siberia and Alaska.

1. Were migrating is the past continuous tense. It implies that something was in process at a certain point of time in the past. This sentence actually wants to discuss what happened in the past, not what was happening in the past. For example:

It is possible that Mughlai cuisine reached India through...
vs.
It is possible that Mughlai cuisine was reaching India through...

2. Existed once between is harder to understand than once existed between. We need the "once-upon-a-time" type of once, not the once-twice-thrice type of once.

She once served as the CEO of a company.
This means that at some (probably distant) time in the past, she served as the CEO of a company.

She served once as the CEO of a company.
This means that she never became a CEO again.

Similarly, the bridge of land once existed between X and Y, not existed once between X and Y.

This is a fairly straightforward and easy question if you don’t overthink this.

There is no need to use the present perfect ‘have migrated’. What we need is simple past ‘migrated’

Eliminate Options A, B, and E based on this.

Compare C and D – D does the better job of clearly stating what happened.

Eliminate C – the preposition ‘to’ is too far away from the verb.

Option D is the best choice.

Hope this helps!

(C) migrated over a bridge of land to the Western Hemisphere that once existed

(D) migrated to the Western Hemisphere over a bridge of land that once existed

Between C and D, the critical difference is the placement of the prepositional phrase ‘over a bridge’. This modifier modifies ‘the land that existed between Siberia and Alaska’ and therefore should be placed close to it. In C, that phrase is placed before the Western Hemisphere, leading to distorted meaning.
That is the reason D is the bull’s eye choice.

'Logical Word order' is an important element of Modification that is such a sly pitfall in high-end SC.

Dear Friends,

Here is a detailed explanation to this question-



A: This answer choice incorrectly uses the present perfect tense to refer to the "Native Americans" action of migrating; the present perfect tense is only used to refer to actions that ended in the past but continue to have an effect on the present. Thus, this answer choice is incorrect.

B: This answer choice incorrectly uses the past continuous tense to refer to the "Native Americans" action of migrating; the past continuous tense is only used to describe actions that were ongoing over a period of time in the past. B also breaks parallelism between " were migrating" and "existed". Thus, this answer choice is incorrect.

C: This answer choice incorrectly modifies the noun "Western Hemisphere" with the phrase "that once existed", implying that the Western Hemisphere no longer exists. Thus, this answer choice is incorrect.

D: This answer choice maintains proper tense usage and conveys the intended meaning of the sentence. Thus, this answer choice is correct.

E: This answer choice repeats the tense error seen in Option B and the error in Option C. Thus, this answer choice is incorrect.

Hence, D is the best answer choice.

To understand the concept of "Present Perfect Tense on GMAT", you may want to watch the following video (~1 minute):



To understand the concept of "Simple Continuous Tenses on GMAT", you may want to watch the following video (~1 minute):



All the best!
Experts' Global Team

(A) have migrated to the Western Hemisphere over a bridge of land that once existed
So they originally migrated in the past and continue to migrate into the future?

(B) were migrating to the Western Hemisphere over a bridge of land that existed once
The sentence wants to say that something happened. What happened? The migration (originally) happened in the past. We need simple past tense; Migrating vs. existed, breaks parallelism; “existed once” suggests that the land existed only one time, but we logically want “once existed,” suggesting something existed at some point in time, but stopped [existing].

(C) migrated over a bridge of land to the Western Hemisphere that once existed
The “that” modifier is restrictive and modifying “Western Hemisphere,” suggesting (nonsensically) the Western Hemisphere once existed.

(D) migrated to the Western Hemisphere over a bridge of land that once existed
bingo

(E) were migrating to the Western Hemisphere over a bridge of land existing once
The sentence wants to say that something happened. What happened? The migration (originally) happened in the past. We need simple past tense;

KarishmaB and other experts,

What is present perfect tense wrong in Option A? For events, that happened in indefinite past we use present perfect over past tense. Then in this case shouldn't present perfect tense be used?

The simple past tense is also called past indefinite. It means an action happened in the past and was over in the past. Since the 'original migration' happened in the past, we use simple past for it. It has no bearing on the present.
We use present perfect to show recency or something that happened at some time in the past with some relation to the present.

For example,

I left it in office. (I did this in the past, at some point)
I have left it in office. (at some time in the past up till now, I left it there)

Did you see the test screening? (when it was going on. Now it is over)
Have you seen the test screening? (It is still going on. Have you seen it yet?)