One Piece of Experimental Evidence That Supports the Idea That

One piece of experimental evidence that supports the idea that the Moon's craters were formed by high-speed impacts is that the craters are round. Another piece of evidence is the:

A) lava that fills each crater, even the small ones.
B) long rays that project from all lunar craters.
C) central peak in the craters.
D) steep walls of the craters, undercut on the side away from the direction in which the Moon is rotating.