Which can be answered by scientific inquiry?

Hellooooo.

I have a couple topics that can either be answered scientifically or not.

· What is the cause of AIDS?
· Are serial killers evil by nature?
· Why is the grass green?
· What is the best recipe for chocolate chip cookies?
· When will the Big Earthquake hit San Francisco?
· How can the maximum yield be obtained from a peanut field?
· Does watching television cause children to have shorter attention spans

I think that 1,3,5,6,7, can be answered scientifically, but I really am not sure.
i know that you can probably find the best recipe using science, but best for one person isn't best for another, and science can't tell you what the 'right' one is. and for the 2nd one, i think it might be a trick question, because right away somebody would probably assume you can't answer it using scientific inquiry, but you are presented with a problem, can form a hypothesis, apparatus, method, conclusion and application, so maybe it could be answered scientifically, with extensive research?

Thanks in advance for your opinions!