Most of the Craters on the Moon Were Created By

Most of the craters on the Moon were created by:

A) debris flying out to the Moon from asteroid impacts on Earth.
B) volcanic activity during the early part of the Moon's history that left old calderas.
C) impacts of fragments of asteroids more or less evenly and continuously over the history of the Moon.
D) impacts of rocky debris during the first billion years of the Moon's history.