Yeah, it's every state. Atoms need a certain quanta of energy to jump to each state of energy, and therefore change state depending on how much energy is absorbed and/or released. This applies to all states of matter.
A. dependent variable
As the the independent variable (i.e. number of cats being sold) increases, the dependent variable (i.e. money made) will also increase. You can have 1,000,000 cats for sale and make no money, but you cannot make money without having sold some cats first.
Hope my weird example helped!
It's D. By "net" they mean the overall force the object experiences, so sum all the force vectors, those in a negative direction (eg friction) should be subtracted.
