A Researcher Wants to Know Whether She Can Encourage Adults

A researcher wants to know whether she can encourage adults to participate in a beneficial amount of aerobic exercise using operant conditioning. She establishes a minimum and a maximum amount of exercise for each participant for each week and the participants are rewarded for each week in which their exercise falls within the desired range. The minimum and maximum amounts are increased gradually over time until the participants are engaged in the desired amount of exercise. This is an example of

A) classical conditioning.
B) an ABA design.
C) a range-bound changing criterion design.
D) a multiple-baseline design.