When a comet nears the sun what happens to its nucleus
it becomes solid
it becomes visible
it disappears
it becomes gas

It becomes gas. 
Comets are objects composed mostly of ice and dust that grow tails when they approach the sun. All comets have a nucleus, which is the hard rock/ice object. When a comet nucleus nears the sun, solar energy begins to heat the ice and vaporize it.

it becomes gas i just took the k12 test the test is called 5.02 Quiz: Asteroids and Comets

The cerebellum is the part of the brain that controls motor coordination.