Question

two critical requirements must be met before light elements, like hydrogen or helium, will fuse and form heavier elements. The two requirements for nuclear fusion are

Answer 1

I had to look for the options and here is my answer:
The two requirements for nuclear fusion that are needed to be met in order for the elements hydrogen and helium fuse to make heavier elements are extremely high temperatures and density. Hope this helps.

Answer 2

Answer:

extremely high temperature and density.

Explanation:

Nuclear fusion occurs in the sun and stars under two conditions: extremely high temperature and density. The high density helps to raise temperatures to 15 million K and that in turn, causes the ionization of hydrogen. The heat causes the ionized nuclei to collide and fuse.