If we examine a ball in free fall, we find that the momentum of the ball is not constant. This is not a violation of the law of conservation of momentum because

Question

A) the force of gravity acts on the ball.
B) the ball experiences an external force.
C) the system is not closed.
D) All of the above.
I think the answer is A because if the system is not closed or the ball experiences an external force it wouldn't be considered law of conservation of momentum. Am I right?