Molly is eating red and black jellybeans from a paper bag. She is not looking at the jellybeans as she eats them. She likes red jellybeans, but she does not like black jellybeans. The amount of jellybeans she has to take from the jar before she gets a red one is never the same. Which of the following statements is true?
A. Molly is on a fixed-interval schedule of reinforcement.
B. Molly is on a variable-interval schedule of reinforcement.
C. Molly is on a fixed-ratio schedule of reinforcement.
D. Molly is on a variable-ratio schedule of reinforcement.