This tough. A and E are the contenders according to me. Not very clear to what "that" refers to. I will simply go with the rule that "that" modifies what ever is closer to it. In this case A would be correct.

Can you explain how "progress" can possibly decimate? May be devastation and enslavement "have" decimated?

Well this sentence is as ambiguous as it can get.
From the meaning point of view E looks the best as progress cannot be desimated ( it sounds awkward )
The sentence would be very clear if it had following construction

For many revisionist historians, Christopher Columbus has come to personify in the name of progress the devastation and the enslavement that have decimated native peoples of the Western Hemisphere.

or

For many revisionist historians, Christopher Columbus has come to personify in the name of progress the devastation and the enslavement that has decimated native peoples of the Western Hemisphere.

It is hard to say whether "devastation and enslavement " is singular or
plural. It depends on how it is used. Both are acceptable. For this reason I stick to A.

Let us hear the OA.

CEO and Chairman Interesting title.

I have questions.

1. Is Devastation and Enslavement .. the same?
2. In A, what does that refer to? Progress? or Anything else?

Regards
Praet

Good Rubuttal! This is the only way by which we are going to learn!!

Is bread and butter the same?
But, we say "Bread and butter is my breakfast"?

I go with a simple rule as to what that refers to.
The nearest noun. But, I see your point. I've been looking
for material that clarifies this confusion. So far, none.

Anyway, let us wait for the official answer.

NO. The "progress" did not do the decimating, the "devastion and enslavement" did.

Here is my 2-cents for whatever it is worth.

A. Wrong specifically because of subject-verb agreement. Also, I don't like the omission of the article "the" when refering to the "devastation..". IMO, Columbus personifies a particular period of incidents of devastation, not devastation and enslavement in general.

B. Wrong because it implies that the native people did the devastating.

C. Wordy and awkward. Also, IMO, the use of the gerund connotes that the devastation is ongoing or recent.

D. Same reason as C.

E. IMO, this is the best choice. First, it has good s-v agreement. (the Bread and butter argument is not relevant because item that are considered to be one entity are treated as singular ("bread and butter IS preferable to bacon and eggs for some dieters, though the latter IS surely more popular", "ham and eggs WAS his choice for breakfast", "black and white IS the favorite color scheme of Soho yuppies". This does NOT apply to "devastation and enslavement", e.g., "the devastion and enslavement were widespread" BTW, while "bread and butter is my breakfast" sounds awkward, "bread and butter are my breakfast" sounds worse. Of course, please take this with a grain of salt as my bread and butter IS not SC.

Finally, since Columbus personifies a particular devastion and enslavement, I think the use of the definite article "the" is appropriate if not mandatory here.
_________________

Best,

AkamaiBrah
Former Senior Instructor, Manhattan GMAT and VeritasPrep
Vice President, Midtown NYC Investment Bank, Structured Finance IT
MFE, Haas School of Business, UC Berkeley, Class of 2005
MBA, Anderson School of Management, UCLA, Class of 1993