ball moving to the left (-x axis) with decreasing speed could be caused by....?

Question

net force to the left with decreasing magnitude
net force to the left with increasing magnitude
net force to the left with constant magnitude
net force = 0
net force to the right with constant magnitude
net force to the right with increasing magnitude
net force to the right with decreasing magnitude

Answer 1

Any net force to the right will decrease the ball's leftward speed. If this decreasing leftward speed goes on forever, the rightward force is decreasing in magnitude. If the force has a constant or increasing magnitude it will eventually reverse the motion.