Right answer choice explanation

I also don't understand why A is the right answer. Can anyone please give an explanation? Looking at the passage again I don't understand how D is wrong. Thank you

I would also like an explanation for A here! Thanks in advance.

It's a bummer this question hasn't been answered yet, it has been over a month since it was first asked. I'd love an answer as to why A is correct too.

^ yes I would also like an explanation

I'm struggling with why answer A is correct. I chose answer D. I'm guessing D is incorrect because it is too narrow in scope as this question deals with a main purpose, but I'm unsure. I would greatly appreciate some insight.

This is a tough question, and while I see how A is right, I was only to convince myself of A after eliminating all other choices. Broadly, the passage is telling us how black historians took an internationalist perspective in an era where mainstream (presumably white) historians had a nationalist perspective- but in their internationalist perspective, these historians were engaging in a form of diaspora-focused nation building. Within this narrative, the second paragraph is explaining a major reason for why these historians took a transnational approach, the question of citizenship. If we look at this as an argument structure question, the second paragraph serves to explain a historical fact that the author cites, and writes about. This understanding is a good match for A, although A is quite loosely worded. As for D, while the fact that some leaders advocated emigration is true, it is ancillary at best to the rest of the passage. It is not the main point of the paragraph, and it is not why the author wrote that second paragraph.