Katrina is trying to put a dollar bill into a vending machine in her office. Sometimes the machine will take a dollar bill on the first try, other times it can take up to five or six tries before the dollar bill is finally accepted. In this example, inserting a dollar bill into the vending machine is reinforced on:.
A. An intermittent reinforcement schedule
B. A continuous reinforcement schedule
C. A noncontingent reinforcement schedule
D. A short-delay reinforcement schedule