What is the first law of thermodynamics?

I- The first law of thermodynamics is a general result that is intended to apply to all natural processes that occur between equilibrium states.
II- Q is the energy transferred (as heat) between the system and its environment, due to a temperature difference between them.
III- W is the work done on the system or by it through forces acting on its boundary.
IV- In an isochoric transformation, the amount of heat received by the gas is completely directed to the variation of its internal energy.
a) Only I and II are correct.
b) Only II and III are correct.
c) Only III and IV are correct.
d) All statements are correct.