Determine which physical conditions are necessary to support nuclear fusion and formation of stars.

The correct approach will be "Increased gravitational attraction".

Explanation:

The increased gravitational attraction seems to be the natural or physical phenomenon that is required to promote nuclear reactions including star formation. This is much more important to establish stars at different temperatures (lower) and greater magnetic pull as well as nuclear fusion tends to happen.

The answer is b because c don't explain why the moths are on them and it isn't a because as we know only one species of moth does this

Answer( precipitate );