Awoman in preterm labor at 30 weeks of gestation receives two 12-mg doses of betamethasone intramuscularly. the purpose of this pharmacologic treatment is to:
a. stimulate fetal surfactant production.
b. reduce maternal and fetal tachycardia associated with ritodrine administration.
c. suppress uterine contractions.
d. maintain adequate maternal respiratory effort and ventilation during magnesium sulfate therapy.