Which of the following is a correct statement of Newton’s second law of motion?

A.     A force acting on a body is proportional to the mass of the body.

B.     The rate of change of momentum of a body is equal to the net external force acting on the body.

C.     The momentum of a body is proportional to the net external force acting on the body.

D.     A force acting on a body is proportional to the acceleration of the body.

B