Wait and signal are the atomic operation possible on semaphore….
Semaphores are integer variables that are used to solve the critical section problem by using two atomic operations, wait and signal that are used for process synchronization…..
The wait operation decrements the value of its argument S if it is positive....
If S is negative or zero, then no operation is performed….
The signal operation increments the value of its argument S….
So, (D) wait, signal ….