(MO)You want to make a film that convinces people to use solar power rather than electricity. Which of the following would best describe your film? Comedy
Propaganda
Documentary
Narrative

Documentary

Explanation:

 Documentary movies are non-fiction movies that document reality. They are usually used to inform the audience of something, to educate them, or call to action. Many documentary movies are socially engaged, which means they present some narrative about a certain problem, ways how to solve it, and people who are dealing with it.

The film idea posed in the question is ecologically engaged. It would include presenting the benefits of solar power, the harm of overuse of electricity, and ways how to switch to the former. That is why the film trying to call for action and convince people of switching to solar power would be a documentary movie.