Answer:
B. blocking I/O
Step-by-step explanation:
Most of the input and output request placed to the computer considers the blocking request. It means that the controls given cannot be returned to the given application until and unless the input/output is complete.
Thus, blocking the input/output does not return till the input and output is complete.
With a blocking I/O, the process is moved to a wait queue when the I/O request is made, and it moved backs to the ready queue as soon as the request is complete, thereby allowing the other processes to run in the meantime.
Thus (B) blocking I/O is the answer.