If the Independent Variable Is Magnitude of Reward, Then Subjects

Multiple Choice

If the independent variable is magnitude of reward, then subjects who experience a large reward say, $200) first may respond less to a small reward say, $20) . This is an)

A) Situation in which to use a within-subjects experiment
B) Example of a contrast effect
C) Example of a concurrent effect
D) Situation in which an experiment cannot be performed