Not only does a conclusion wrap up the main points and cause the reader to think about the essay in a different way in a research paper, but in any type of paper. It simply gives your essay a satisfying conclusion and causes your reader to think about your essay in a more meaningful and impacting way. Such a conclusion basically makes any paper, no matter what its type, better. None of the other answer specifically does this, and just as a rule of thumb, a good conclusion NEVER introduces new sources of information, i.e. talks about something that wasn't previously mentioned, so answer choices like those should be crossed off of your list immediately.
If sentence #2 was a standalone, we wouldn't know why tutors would develop egos, but with the info #1 provides us, we know why they feel superior to their students.
