In Polling I/O, the Main Inefficiency Comes from

Multiple Choice

In polling I/O, the main inefficiency comes from

A) the hardware controller when it notifies the CPU that the device is ready for service.
B) the basic polling operation that may be comprised of several CPU instructions.
C) polling when it is attempted repeatedly yet rarely finds a device ready for service.
D) the slow data transfer rate between a device and the host.