Assertion (A): Social mobility is the movement of individuals or groups from one social stratum to another.
Reason (R): The degree to which systems of stratification are open or closed depends on the extent of social mobility.

A. Both A and R are true and R is the correct explanation of A

B. Both A and R are true but R is not a correct explanation of A

C. A is true but R is false

D. A is false but R is true

Answer: Option C