Which Research Design Tests for the Effect of Motivation on Behavior

Which research design tests for the effect of motivation on behavior?

A) Pigeons' performance accuracy on a three-sample DMTS is compared with another group's performance on a ten-sample DMTS task.
B) A dog receives a three-second shock every time a buzzer sounds, but no shock when a flashing light is turned on.
C) Running speeds and performance accuracy in a maze study using rats are compared at the beginning, midpoint, and end of training.
D) A rat is given fifteen pellets for pressing the left-hand lever eight times, and given three pellets for pressing the right-hand lever two times.