c1q1=Smoking cigarettes changes ______.&c1a1_a=the amount of a brain chemical that allows us to experience pleasure&c1a1_b=the amount of blood that flows to the brain&c1a1_c=the number of things we worry about&c1a1_correct=a&end_c1q1=1

&c1q2=In the brain, nicotine locks into receptors on neurons, making the smoker feel _______.&c1a2_a=irritable&c1a2_b=sleepy&c1a2_c=alert and satisfied&c1a2_correct=c&end_c1q2=1

&c1q3=After a while, the brain shuts down some receptors so a smoker needs a cigarette _______.&c1a3_a=to stop cravings&c1a3_b=just to feel normal&c1a3_c=both a and b&c1a3_correct=c&end_c1q3=1

&num_c1=3&end_c1=1