Answer:

Big Bang Theory - according to this theory, a singularity in the beginning of time suddenly exploded and expanded rapidly and coming out of it are matter which soon transformed into everything we see around us today.

Steady State Universe Theory - this theory states that there is a continuous creation of matter, and that the universe has no beginning or end.

Eternal Inflation Theory - this theory states that the universe keeps on expanding, and new universe are being created as it expands further. It also says that our universe might one of the many multiverses that co-exists.