D. All of the above
Each of these points provides evidence that supports the Big Bang theory and the idea that the universe originated from a singularity:
A. Cosmic microwave background radiation (CMB) is the remnant radiation from the hot, dense state of the early universe, providing evidence of the conditions shortly after the Big Bang.
B. Redshift of light from distant galaxies indicates that the universe is expanding. This expansion suggests that galaxies were once much closer together, consistent with the idea of a singularity.
C. The universe is expanding means that it was once smaller and denser, consistent with the concept of a singularity at the beginning of the universe.
All of these pieces of evidence collectively support the Big Bang theory and the idea of a singularity as its origin.