Question

which is a thesis statement?
despite government subsidies for renewable energy, coal remains one of the united states largest sources of electricity.
this paper discusses why solar energy is a better source of power than coal.
solar energy is a better source of power than coal because it is clean and renewable.

Explanation:

A thesis statement presents a claim and reasons. The first option is a fact. The second describes the paper's content. The third ("Solar energy is a better source of power than coal because it is clean and renewable") makes a claim (solar is better) and provides reasons (clean, renewable), fitting a thesis statement.

Answer:

Solar energy is a better source of power than coal because it is clean and renewable.