Evidence suggests that during wakefulness a sleep-promoting chemical is produced and builds up in the blood until the person becomes tired and falls asleep.

Infants begin to form an emotional attachment to their mothers or a surrogate mother at ______ .

A) birth B) about 3 months C) about 6 months D) about 1 year

Prenatal exposure to tobacco from a mother who smokes cigarettes is not really a problem since the baby's lungs are not exposed to the smoke until after it is born.

a. true b. false