25 !
a baby's first breath initiates a series of changes that includes which of the following?

a. the ductus venosus and ductus arteriosus both open.
b. the ductus venosus and ductus arteriosus both close.
c. the ductus venosus opens, and the ductus arteriosus closes.
d. the ductus venosus closes, and the ductus arteriosus opens.

The primary factor that initiates breathing in newborns is the need for oxygen. The fetus actually practices breathing while still in the womb. So spanking them on the butt once they are born is totally unnecessary and no longer practiced. The newborn will take its first breath when it needs it, as long as the airway is clear. That is why one of the first things they do after a baby is born is to use a syringe to empty the airways of amniotic fluid. The rest is up to nature and instinct to take over and the baby will start breathing on their own.