Question

the time from last menstrual period to the birth of the baby (~280 days)
gestation
regurgitation
copulation
parturition

Explanation:

Gestation is defined as the period from the last menstrual period to the birth of the baby (about 280 days in humans). Regurgitation is the act of bringing swallowed food back to the mouth. Copulation is sexual intercourse. Parturition is the act of giving birth, not the entire period leading to it. So "gestation" matches the description.

Answer:

A. gestation