Answer
See the detailed answer below.
Work Step by Step
a) See the figures below, and recall that: $F_G\rightarrow$ Gravitational force.
b) The acceleration here is the free-fall acceleration which must be downward. The object here is moving under the free-fall acceleration and there are no other forces exerted on it.
c) The direction of the speed is not clear here since it can be slowing down while moving up or speeding up while moving down. It could also be moving in a trajectory.
d) A baseball is moving in the air after a massive shot from the player.
