Assertion (A): Doping level in extrinsic semiconductors is very small. Reason (R): Additional of impurity in the ratio of 1 part in 108 parts increases the number of charge carriers by about 20.

• Both A and R are true and R is correct explanation of A
• Both A and R are true but R is not correct explanation of A
• A is true but R is false
• A is false but R is true