Well based on the three I would think it's C
Answer:

Explanation:
Case 1
Given,
initial angular speed = 0 rev/s
final angular speed = 2 rev/s
time, t = 7 s
angular acceleration of the washer



using equation of rotational motion



Case 2
Given,
initial angular speed = 2 rev/s
final angular speed = 0 rev/s
time, t = 12 s
angular acceleration of the washer



using equation of rotational motion



total revolution in this case



total revolution of the washer is equal to 20 rev.
D it is D the answer is D
I think this might be the answer let me know 0.2 g/cm^3
If one reverse the orientation of a permanent magnet ITS MAGNETIZATION WILL BE PERMANENTLY REVERSED. This is because, the magnetic domains inside the permanent magnet aligned with the new applied field and increase with it while those domains that are anti aligned with that field will shrink.