The theory of the origin of the universe which began as a hot, dense state highlighted by rapid expansion.
A. Singularity
C. Rapid Expansion
D. Inflation
The Big Bang theory says that the universe came into being from a single, unimaginably hot and dense point (aka, a singularity) more than 13 billion years ago. It didn't occur in an already existing space. Rather, it initiated the expansion—and cooling—of space itself.