Which Statement About a Condition of Pregnancy Is Accurate

Which statement about a condition of pregnancy is accurate?

A) Insufficient salivation (ptyalism) is caused by increases in estrogen.
B) Acid indigestion (pyrosis) begins early but declines throughout pregnancy.
C) Hyperthyroidism often develops (temporarily) because hormone production increases.
D) Nausea and vomiting rarely have harmful effects on the fetus and may be beneficial.