The answer is A. “Researchers' estimates of the actual number vary from three hundred to six thousand, but everyone knows that ads are everywhere.” (paragraph 1)
Explanation:
Conjunctions link grammatical elements. In the case of the coordinating conjunctions, which includes and, but, or, yet, etc., these are mainly used to coordinate or join elements of the same rank. This applies to complete ideas known as independent clauses, which creates compound sentences.
This can be seen in sentence A because this contains the coordinating conjunction "but". Also, you can know this is a coordinating conjunction because each of the clauses "but" joins is a complete idea or independent clause.
You would C., begin the research process a second time, because DEFINITELY in a research paper/topic you need the MOST information, facts, and details about your topic to really inform as much as possible to your readers about your topic! If it's a lil relevant and too general to give specific support, that shows you need to rewrite your paper, as you may get scored poorly as it does not sufficiently answer the prompt.
I hope I helped! ;-;