The Cassini Division Was Observed in 1675 as a Visible

The Cassini division was observed in 1675 as a visible gap between Saturn's A and B rings. What we have discovered since then is that the Cassini division:

A) is completely empty, which we observed when the Cassini spacecraft flew through this gap.
B) contains a small number of tiny particles, which we observed by bouncing radio waves back to Earth from this gap.
C) contains a small number of tiny particles, which we observed by imaging the division from the back (shadow) side with the Cassini spacecraft.
D) contains a small number of large boulders, which we observed by watching the reflection change as the boulders tumbled in the sunlight.