What best supports the concept of the big bang theory?

The concept of the Big Bang Theory is best supported by three key pieces of evidence: the observable expansion of the universe, the cosmic microwave background radiation, and the abundance of light elements. The redshift of distant galaxies indicates that the universe is expanding, suggesting that it originated from a singular point. The cosmic microwave background radiation is the remnant heat from the initial explosion, uniformly detected across the universe. Additionally, the predicted ratiOS of hydrogen, helium, and lithium align with observed abundances, further corroborating the theory.