Answer: D
Key thing to keep note, is "refraction"...
Look at some experiments on YouTube, it's helps me a lot.
Answer:
Angular acceleration, is 
Explanation:
Given that,
Initial speed of the drill, 
After 4.28 s of constant angular acceleration it turns at a rate of 28940 rev/min, final angular speed, 
We need to find the drill’s angular acceleration. It is given by the rate of change of angular velocity.

So, the drill's angular acceleration is
.