I believe the answer to be A) because distance with the time it took to to reach the distance would determine how speed is to be calculated.
The CPU, or central processing unit, is the hardware that takes most of the load when running a program. It will perform complex calculations and execute every instruction as the program continues.
The GPU, or graphics procession unit, is the hardware that could also play a major roll in calculating the instructions to execute a program, though this depends on how graphically intensive the program is. For example, games would use a lot more GPU power than say a simple calculator application.
Answer is the son-father-grandfather concept. Good luck
