When We See a Region of a Planet That Is

When we see a region of a planet that is not as heavily cratered as other regions,we conclude that

A) there is little volcanic activity to create craters.
B) the planet is rotating very slowly and only one side was hit by impactors.
C) the planet formed after the age of bombardment and missed out on getting hit by leftover planetesimals.
D) the surface in the region is older than the surface in more heavily cratered regions.
E) the surface in the region is younger than the surface in more heavily cratered regions.