When you read or watch another source for your assessment, is it always necessary to read or watch all of it$?$

Question $2$ options:

No$.$ It is sufficient to skim through it

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

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

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