Look for books in the section where your research paper is based on
Answer:
B. My cousins care too much about appearances
These lines from Act III are important in the plot of the play because it gives importance to the time of the murder and also to the people involved. It is the time at which the ghost disappears and then again reappears after the lines to create a great suspense, which should get the reader hooked. (Hopefully the lines you were talking about, where the ones I was thinking about)
I don't know because you didn't give me options