A Boy Is Teaching His Younger Sister How to Make

Multiple Choice

A boy is teaching his younger sister how to make her bed.At first,he tells her that she did a good job when she gets the bedspread pulled up,even if the sheets are still rumpled.Each following day,he encourages her to be a little neater before telling her that she did a good job.Which term best characterizes this approach to learning?

A) secondary reinforcement.
B) primary reinforcement.
C) a fixed-interval schedule.
D) shaping.