Stewart is a musician and often takes "meth" before his performances to help give him an "edge." Recently he has found that when he hasn't had a performance for several days and thus has not taken "meth," he begins to feel fatigued and dragged out. He becomes high, agitated, and can't concentrate on his music. Stewart is demonstrating ____

a. an addiction
b. symptoms of withdrawal
c. psychological dependence
d. tolerance

b