Answer:
Green means, "good for the environment" and "not wasteful".
It's green because it is a natural, renewable, and plentiful energy source.
Cost don't quite matter, because (for instance) solar panels are good for the environment due to the fact that they provide green energy, but it still costs. So, the first answer is incorrect.
True, it probably doesn't require farming, but that doesn't make it "green".
It can work at night, because there can still be wind at night.
When you burn things, it releases gas and carbon dioxide into the air, contributing to global warming or the greenhouse effect. If it were to be burned, then it would not be "green". Wind energy doesn't require burning anything, so the answer is D. The fact that it doesn't require burning anything can make it green.