Answer:
D: Scan each source to see whether it relates to your research question.
Explanation:
Why are the others incorrect?
Well, A says to compare the sources, and only use the shortest ones. That's not helpful. While some valuable information may well be in short sources, that doesn't mean you need to exclude the longer ones.
B says to assume that all search results represent useful sources of information. That's not going to fly, either. Search engines can't always be trusted. But, C says to read each word for word as soon as you find it. That'll take too much time, however. And, it won't come in handy later.
So, D: Scan each source to see whether it relates to your research question is correct.
