What is the Jeans instability?

A When a growing protoplanet becomes too large, it is more likely to be split apart by subsequent bombardment than to grow further.

B If a solar nebula is too massive it will continue to collapse to become a black hole and will not form planets.

C If the disk of matter surrounding a solar nebula becomes too hot, it will dissipate, and planets will not form.

D If a cloud of gas and dust is sufficiently dense, it will collapse due to its own gravity.