Which statement about enthalpy is true?
a. The enthalpy of formation for a pure element in its standard state is always positive.
b. The enthalpy of formation for a pure element in its standard state is always negative.
c. Enthalpy is a state function because its change depends only on initial and final conditions.
d. Enthalpy is not a state function because its change depends on the identities of the reactants and products.