The BEST Estimate for the Time of Production of Most

Multiple Choice

The BEST estimate for the time of production of most craters on both Mercury and the Moon is

A) relatively recently, about 4 billion years after planet formation.
B) in the first 800 million years after planet formation.
C) about halfway through their lives, or about 2.3 billion years after planet formation.
D) at a relatively constant rate throughout their lives, up to and including the present day.