A convergent – divergent nozzle may give supersonic or subsonic flow

Question

 Assertion (A): A convergent – divergent nozzle may give supersonic or subsonic flow at the exit even if the throat is chocked.                        

Reason (R): Depending on the back pressure ratio p_b/p_o, the divergent part of the nozzle may act as a supersonic nozzle or a subsonic diffuser.

1. Both A an R are individually true and R is the correct explanation of A
2. Both A and R are individually true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true