A rocket launches because of . A. an opposite reaction
B. it's large mass
C. its gravity
D. air resistance

an opposite reaction

Earth's gravity is still pulling down on the rocket. When a rocket burns propellants and pushes out exhaust, that creates an upward force called thrust. To launch, the rocket needs enough propellants so that the thrust pushing the rocket up is greater than the force of gravity pulling the rocket down.

A, an opposite reaction

Hope this helps :)

beta decay is the answer