The right answer for the question that is being asked and shown above is that: "narrowing your topic." the strategy that involves looking through reference materials and jotting down each interesting person, place, object, or event you come across is that narrowing your topic
The answer is B. You should always proof read your paper. D is a good answer too, but I'm pretty sure they want B as the answer. If I'm wrong, then sorry. It's just what I've been taught. Proofread at least two or three times.
"This part of the country"
"western" vs "east" also denotes location, which implies that a region is a specific location in a "part of the country"