When disc B is brought in contact with disc A, they acquire a common angular velocity in time t. The averagefrictional torque on one disc by the other during this period is

A

$$\frac{2 I \omega}{3t}$$

B

$$\frac{9 I \omega}{2t}$$

C

$$\frac{9 I \omega}{4t}$$

D

$$\frac{3 I \omega}{2t}$$