Question

which piece of evidence is relevant to the explanation that a big bang explosion occurred?
a the universe is expanding
b large amounts of microwave radiation mixed within earth
c several different forms of elements that make up the universe were found

Explanation:

• The Big Bang theory suggests that the universe originated from a singularity and has been expanding ever since. The observation that the universe is expanding (Hubble's law - galaxies are moving away from each other) supports the idea of an initial explosive event (the Big Bang) that set the expansion in motion.
• Option B is incorrect. Cosmic microwave background radiation (CMBR) is a remnant of the Big Bang, but it is spread throughout the universe, not "mixed within earth".
• Option C is not a direct piece of evidence for the Big Bang. While the Big Bang theory can explain the abundance of light elements (like hydrogen and helium), just finding elements in the universe is too vague and not a key - specific evidence for the Big Bang explosion.

Answer:

A. The universe is expanding