Answer: Option A; 9.8 m/s^2
Step-by-step explanation:
When an object is in the air, and there is no air resistance acting on the object, the only force that will act on the object is the gravitational force (on the vertical axis).
Then, if the only force acting on the object is the gravitational force, the acceleration of the object will be equal to the gravitational acceleration.
We know that the gravitational acceleration is equal to:
g = 9.8m/s^2
Then the acceleration on the vertical axis will be equal to:
a(t) = 9.8m/s^2
The correct option is the first one:
A. 9.8 m/s^2