Piece of code that only one thread can execute at a time is called ...

Piece of code that only one thread can execute at a time is called

Answer : b.  Critical Section

The critical section is a code segment where the shared variables can be accessed. An atomic action is required in a critical section i.e. only one process can execute in its critical section at a time. All the other processes have to wait to execute in their critical sections.

By: Brijesh Kumar