The correct answer is A) a token economy.
Although the results are mixed, a token economy has often been used by teachers who are eager to instill order in an unruly classroom.
One of the techniques people use in contingency management is a token economy to reinforce an expected behavior. The token is the symbol that is going to be used to exchange it for the expected behavior. In school, for instance, teachers use stickers with the figures of stars, the sun or animals to give their students when they do something correctly.
The other options of the question were B) programed learning. C) biofeedback training. D) physical punishment.