A Thread Using POSIX Condition Variables, a Thread

Multiple Choice

A thread using POSIX condition variables, a thread

A) must lock the associated mutex lock before calling pthread_cond_wait( ) and unlock it after calling pthread_cond_signal( ) .
B) must lock the associated mutex lock before calling pthread_cond_wait( ) , but doesn't need to unlock it after calling pthread_cond_signal( ) .
C) doesn't need to lock the associated mutex lock before calling pthread_cond_wait( ) , but must unlock it after calling pthread_cond_signal( ) .
D) doesn't need to lock the associated mutex lock before calling pthread_cond_wait( ) and doesn't need to unlock it after calling pthread_cond_signal( ) .