If the net force on an object in uniform motion is zero, the object will _____.

The correct option is B remains in its state of motion (rest or moving with constant velocity)
According to Newton's first law of motion, an object remains in a state of rest or of uniform motion in a straight line unless compelled to change that state by an applied force'.
In the absence of a net force, there will be no change in velocity of the object. Therefore, the object in motion or rest, remains in its original state of motion.