For the equilibrium process $H_2O_{(\ell)} \rightleftharpoons H_2O_{(g)}$ at $1 \, \text{atm}$ and $373 \, K$,which of the following is true?

• A
  Standard free energy change is zero $(\Delta G^o = 0)$
• B
  Free energy change is zero $(\Delta G = 0)$
• C
  Free energy change is less than zero $(\Delta G < 0)$
• D
  Free energy change is greater than zero $(\Delta G > 0)$