The ________ Multithreading Header Contains Classes, a Function and an Enum

The ________ multithreading header contains classes, a function and an enum that are used together with facilities in header <mutex> to implement thread synchronization. In particular, condition variables can be used to make threads wait for a specific condition in a program, then to notify the waiting threads when that condition is satisfied.

A) <thread>
B) <mutex>
C) <condition_variable>
D) <future>