Aball is thrown straight up from the ground. what way does its acceleration point at the top?
a. vertical
b. horizontal
c. it isn’t accelerating
d. horizontal and vertical

A. Vertical

Explanation:

If the ball is thrown straight up from the ground (asuming the ground as height 0), this means its initial velocity is greater than zero.

While the ball rises and gains height, its velocity decreases until it reaches its maximum height where it stops (velocity equal to zero) and then it begins to fall to the ground.

Now, during all the movement, the ball has an acceleration, which is the acceleration due gravity (9.8 m/s^{2}  on Earth), even at the top or maximum height (when the ball stops just for fraction of time), and this acceleration points vertical and downward to the Earth's center.