Concept:Projectile motion has independent horizontal and vertical components under the action of gravity.
Explanation:Neglecting air resistance, no horizontal force acts on the ball after projection.
Therefore, its horizontal velocity remains constant throughout the motion.
Gravity acts vertically downward with a constant acceleration
g.
Hence, the vertical acceleration of the ball is constant.
The vertical velocity is not constant; it increases as the ball falls downward.
Thus, statement I is incorrect, statement II is correct, and statement III is correct.
Answer:D. II and III only