The Small Sacs of the Newborn's Lungs Are Forced Open

The small sacs of the newborn's lungs are forced open by the

A) squeezing of the fetus's body as it moves through the birth canal.
B) birth cry after the fetus exits the birth canal.
C) squeezing of the fetus's head as it passes through the mother's pelvic bones.
D) vigorous rubbing of the newborn's body by the medical staff immediately following birth.