This is significant because the absence of everyone else marks how few friends Gatsby really had. For all the people he knew and entertained, only Nick and a man who admired Gatsby's library were in attendance. This is also significant because it illustrates how few true friends we are actually blessed with during our lifetimes
This is probably a joke but I'll answer anyway
By 'cheeks' they mean buttocks so by "making them clap" is referring to them being so big/thick that they clap or make noise when you walk or move around or something.
I probably got played lol but whatever
the answer too your question is A.
D. Wide angle lens
An overview shot is when you want to take a picture of an entire thing A wide angle lens allows this to happen