What key is Scar Tissue in and how do you know?

Heya. I'm trying to figure out what key Scar Tissue is in and I've managed to narrow it down to the following:


C Major


D Minor


F Major





I'm leaning towards C Major but this is the first time I have tried to work out a key.





What key is it in?





Thanks.

What key is Scar Tissue in and how do you know?
F major i think.