Question

The universe cooled after the Big Bang. At some point, hydrogen atoms combined to form helium. What is this process called?

Answer 1

Answer: fusion

Explanation:

Nuclear fusion is a process which involves the conversion of two small nuclei to form a heavy nuclei along with release of energy.

$4_1^1\textrm{H}\rightarrow _2^4\textrm{He}+2_{+1}^0\textrm{e}+\text{energy}$

Nuclear fission is a process which involves the conversion of a heavier nuclei into two or more small and stable nuclei along with the release of energy.

Red shift is a phenomenon where electromagnetic radiation from an object undergoes an increase in wavelength.

Nuclear decay is a type of process in which a less stable nuclei decomposes to a stable nuclei by releasing some radiations or particles like alpha, beta particles or gamma-radiations.

Answer 2

A) nuclear fusion is the answer