Which One of the Following Is an Example of Reinforcing

Which one of the following is an example of reinforcing an incompatible behavior as a way of eliminating an undesirable behavior?

A) Samantha is very shy and socially withdrawn. Her teacher reinforces her with a smile whenever she interacts with her classmates.
B) Johnny's wisecracks have become so annoying that his teacher keeps him in from recess whenever he speaks inappropriately.
C) Mary has learned to reinforce herself whenever she gets all her spelling words correct.
D) Jerry must stay after school on days when he arrives late.