Your Questions About Solar Energy Generator Wikipedia

How Efficient is oil?

I have science homework which is handed in on Thursday 5th January 2012 and it is to gain a merit level. I am stuck on A lot of questions. These are the questions:

How Efficient is oil energy?

How Efficient is hydroelectric energy?

What effects does oil energy have on the environment?

What effects does coal energy have on the environment?

What effects does gas energy have on the environment?

What effects does hydroelectric energy have on the environment?
What effects does wind energy have on the environment?

What effects does solar energy have on the environment?

Thanks for helping.

How green are cars like the volt really, i mean you plug it in the wall that use energy likely from coal?