What Is the Expression for K_c for the Following Equilibrium $\rightleftharpoons$

What is the expression for K_c for the following equilibrium?
CaSO₃(s) $\rightleftharpoons$ CaO(s) + SO₂(g)

A) $[ \mathrm { CaO } ] \left[ \mathrm { SO } _ { 2 } \right]$
B) ? $\left[ \mathrm { SO } _ { 2 } \right]$
C) ? $\frac { [ \mathrm { CaO } ] \left[ \mathrm { SO } _ { 2 } \right] } { \left[ \mathrm { CaSO } _ { 3 } \right] }$
D) ? $\frac { \left[ \mathrm { CaSO } _ { 3 } \right] } { [ \mathrm { CaO } ] \left[ \mathrm { SO } _ { 2 } \right] }$
E) ? $\frac { 1 } { \left[ \mathrm { SO } _ { 2 } \right] }$