A projectile is launched from level ground at an angle of $45^{\circ}$ above the horizontal. Air resistance is negligible. Which row gives the horizontal motion and the vertical motion of the projectile from just after launch until just before it lands back on the ground?
- Ahorizontal motion: constant velocity; vertical motion: constant acceleration
- Bhorizontal motion: constant velocity; vertical motion: varying acceleration
- Chorizontal motion: varying velocity; vertical motion: constant acceleration
- Dhorizontal motion: varying velocity; vertical motion: varying acceleration