The primary explanation for the addictive nature of street drugs lies in their impact on the brain's ________ system

Because it had to be administered ________, the Stanford-Binet Intelligence Scale was not as ________ as other intelligence tests

a. in groups; standardized b. individually; economical c. quickly; valid d. often; reliable e. only one time; consistent

Cesarean sections

a. should not be performed when a fetus is in distress. b. are less risky than vaginal deliveries for mothers. c. pose little risk for babies. d. can interfere with later mother-baby interactions.