I just took a test in school today. What question was I asked?

Question I was asked: What part of the water cycle takes place when water from clouds falls back to Earth?

I just took a test in school today. What question was I asked?

Question I was asked: During a lecture, a professor was talking about the potential that hydrogen has for exploding under certain conditions. Which was most likely the topic of the professor's lecture?

I just took a test in school today. What question was I asked?

Question I was asked:
The source of energy for the Earth's water cycle is the