Close binary star systems are thought to form when
A) two interstellar gas clouds happen to contract so close together that there's no room for a disk or planets.
B) the protostellar disk around a protostar has enough material to form a second star.
C) gravity pulls two neighboring protostars quite close together, but angular momentum causes them to orbit each other rather than colliding.
D) a protostar emits two jets, each of which turns into a star.
Answer: C