The geometry question could be A or B. Unless you don't want the degenerate line segment triangle of course, then only A.

I think the algebra problem might be C, but I'm shaky on that one.

By my reckoning the last answer is C, but I did it like a simple geometry problem by considering the coating as a cube with edge length 4.2 minus a cube with edge length 4.

By the way, where do you get these? Are you writing them yourself, copying them out of a book, or are these actual schoolwork quiz problems?