Treating this as a straight-line motion problem, the following formula can be used to solve for acceleration:
Vf = Vi + at
Where: Vf = final velocity = 0 m/s
Vi = initial velocity = 15 m/s
a = acceleration = ?
t = time = 0.75 s
Substituting the given values:
0 m/s = 15 m/s + a * 0.75 s
|a| = -15 / 0.75
a = 20 m/s^2
Therefore, the answer is A.