Occasionally, Babies Are Born with a Tiny Hole Between Their

Occasionally, babies are born with a tiny hole between their left and right atria. Usually, the hole closes during early childhood, but if not, the child must undergo surgery to close the hole. Why is this hole likely to be a problem?

A) The hole would weaken the muscles in the atria, making it difficult for them to pump blood to the body.
B) The hole would allow blood in the left ventricle to be pushed backward into the right atrium rather than being pumped to the body.
C) The hole would allow the mixing of oxygenated and nonoxygenated blood, decreasing the efficiency of the cardiovascular system.
D) The hole would prevent any blood from reaching the lungs.