One of Your Friends Routinely Uses "Study Pills" (Ritalin) to Help

Multiple Choice

One of your friends routinely uses "study pills" (Ritalin) to help him stay awake and pull all-nighters during exam time. Normally, if he takes a small dose, he is fine, but lately when he takes the same dose, he gets extremely agitated and cannot sit still. The same dose is having a larger effect on him than it used to. This is an example of:

A) drug addiction.
B) tolerance.
C) behavioral sensitization.
D) withdrawal.