Question $2$: Two projectiles are in flight at the same time. The acceleration of one relative to the other:

A$)$ is always $9\mathrm{.}8\frac{m}{s^2}$

B$)$ can be as large as $19\mathrm{.}6\frac{m}{s^2}$

C$)$ can be horizontal

D$)$ is zero

E$)$ none of these