What is the primary reason why scientists accept the Big Bang Theory as the origin of the Universe?

Question

A.
Studies of the motion of galaxies show that the universe is expanding

B.
Studies of the motion of galaxies show that the universe is collapsing

C.
Studies of the motion of galaxies show that the universe isn’t moving

Answer 1

The primary reason why scientists accept the Big Bang Theory as the origin of the Universe is:

A. Studies of the motion of galaxies show that the universe is expanding.

This observation, particularly the redshift of light from distant galaxies, supports the idea that the universe has been expanding since its inception, which aligns with the predictions made by the Big Bang Theory.