The question needs a little more clarification. Communism and Socialism according to whom? Are we talking about Marx's conception of history and how he viewed socialism and communism on that historical path? Also, because you specifically mention an exam, I have to imagine there have been some course readings or assignments on the topic beforehand. You're best bet is to consult those materials rather than looking for outside ones if possible, because the test is going to be looking for something specific, I'd imagine.

Alternatively and in fact probably preferably, you can go to your professor's office hours and ask him or her to give you some advice about where to look, because you will get a much more direct answer that will pertain to the class much more effectively than we can here.

This is a political question rather than a historical one. Have you tried asking over at r/socialism?