We Know That There Are Large Gaps in the Average

Multiple Choice

We know that there are large gaps in the average distances of asteroids from the Sun (within the asteroid belt) because we

A) see the gaps through telescopes.
B) see the gaps via stellar occultation.
C) know they are there theoretically,although we haven't detected them.
D) actually don't know whether there really are gaps or not.
E) have plotted distributions of the orbital radii of the asteroids.