The Rate of Cratering

Multiple Choice

The rate of cratering:

A) has remained constant over the last 4.6 billion years.
B) has recently increased with more collisions in the asteroid belt.
C) fluctuates over time, with massive bodies occasionally coming in from the Oort Cloud.
D) shows that large asteroid impacts are more common now than in the past.
E) shows that most interplanetary debris was swept up soon after the formation of the solarsystem.