Which of the following best describes the geological histories of the Moon and Mercury?
A) All four geological processes were important in their early histories, but only impact cratering still reshapes their surfaces today.
B) Impact cratering is the only major geological process that has affected their surfaces.
C) Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.
D) Impact cratering shaped these worlds early in their histories. Then, during the past few million years, they were reshaped by episodes of volcanism and tectonics.
Answer: C