Aiden takes 0.10 s to throw a baseball, which leaves his hand with a velocity of 40 m/s. the ball's acceleration is

Acceleration (A) = V(final)-V(initial)/TThe unit for acceleration is metres/second squared (m/s^2).

You're already given Velocity (V) = 40 m/s in the question, so just plug in the values.

A= 40/0.10
A= 400 m/s^2. 

A) acceleration. this seems to be the one that makes sense.

The independent variable would be the fertilizer as it is what the dependent variable (the growth of grass) depends on.