Question

The ___ theory says that the moon formed from the dust produced by a collision between earth and another large body.

Answer 1

B, the impact theory says that 

Answer 2

B. impact

The impact theory says that the moon formed from the dust produced by a collision between earth and another large body.  The theory hypothesized that a planet like body collided with Earth and was named as Theia. The released particles containing dust combined to create moon.