Answer:
The baby starts breathing
Explanation:
While in the womb, a fetus has its oxygen delivered to it, and the waste products removed (all via the mother's bloodstream), so there is no reason to separate all the chambers of the heart while still in the womb.
However, once the baby is born and it is breathing, the chambers need to differentiate in order to allow the blood to reach the lungs, and the oxygenated blood and deoxygenated blood do not mix.
First I would have my friend call an ambulance while I checked his pulse. After this, I would most likely have my friends call for help in the hallway. Then I would try to put him against the wall in an upright position. Then I would try to get a response out of him whether verbally or physically. After this, I would wait for an ambulance to get there while sitting him up and trying to wake him up at the same time.
A persons biological because its the only one that makes sense according to the study of genetics. EX: X chromosome are always in females eggs, while the x & y chromosome is in the male.