The best statement that describes the effect of the net force applied to a moving object is:
The force will cause a change in the momentum of the object.
This is because a net force acting on an object results in an acceleration, which according to Newton's second law (F=ma), will change the object's velocity. Since momentum is the product of mass and velocity (p = mv), any change in velocity (whether in speed or direction) will indeed lead to a change in momentum.