Most Craters on Mercury Appear to Have Been Produced By

Most craters on Mercury appear to have been produced by:

A) impacts from objects from space early in the planet's history.
B) successive expansion and contraction of the planet's surface because of intense heating by the Sun and severe cooling during rotation because the craters appear to be in irregular lines across the surface.
C) volcanic eruptions early in the planet's history.
D) continuous impacts by objects from space throughout the planet's history, including very recently in geological time.