What Keeps the Moon Moving, I

What keeps the moon moving, i.e., why doesn't the moon slow down and stop?

A) Nuclear processes operating in the central core of the moon.
B) It is the natural motion of every object to keep moving by itself.
C) Earth's gravity keeps it moving.
D) The sun's gravity keeps it moving.
E) It actually is slowing down, and will come to rest in a few thousand more years.