The correct answer is B. CPU cycle.
A CPU cycle is the basic time unit of a computer’s operation. It is the time it takes for the CPU to fetch an instruction from memory, decode it, and execute it. The number of CPU cycles per second is called the CPU’s clock speed.
Delay time is the time it takes for a signal to travel from one point to another in a computer system.
Real time is the actual time that passes, as measured by a clock.
Seek time is the time it takes for a disk drive to move its read/write heads to the correct location on the disk.
None of the above options are the time required for the fetching and execution of one simple machine instruction.