When you read or watch another source for your assignment, is it always necessary to read or watch all of it?单项选择题

a. No. It is sufficient to skim through it

b. Yes. You might miss something if you don't. You should also note the reference

c. No. You should find the most useful parts and read or watch those. You should also note the reference

d. No. It's enough just to read or watch the introduction and note the reference