An electron, starting from rest and moving with a constant acceleration, travels 2.0 cm in 5.0 ms. what is the magnitude of this acceleration?

 s=2.7 centimeters = 0.027 meters 
t=3.9 milliseconds = 0.0039 seconds 

s=(1/2)a*t^2 
so 
a=(2.7*2)/(0.0039)^2 
= 355,029.58 m/s^2 

a=355,029.58 m/s^2 = 355.02958 km / s^2

Ithink the answer is a

The answer is d) by requesting advice on science internet sites