In the Equation Relating Equilibrium to Thermodynamics, a = -RTb $\Delta$

In the equation relating equilibrium to thermodynamics, a = -RTb,

A) a = $\Delta$ G and b = lnK.
B) a = $\Delta$ G $\degree$ and b = K.
C) a = $\Delta$ G $\degree$ and b = lnK.
D) a = $\Delta$ G $\degree$ and b = K
E) a = ln $\Delta$ G $\degree$ and b = K