For the reaction $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$, the relationship between $K_p$ and $K_c$ is:

General relation: $K_p = K_c \cdot (RT)^{\Delta n}$, where $\Delta n$ is the change in gas-phase moles, $n_{products} - n_{reactants}$. For the SO₂ oxidation: products $2$ mol of SO₃; reactants $2 + 1 = 3$ mol. So $\Delta n = 2 - 3 = -1$. $K_p = K_c \cdot (RT)^{-1} = \dfrac{K_c}{RT}$. Quick sanity rule: when products have fewer gas moles than reactants, $K_p < K_c$ (at usual conditions where $RT > 1$). Option D would require $\Delta n = +2$, which would mean two more product gas moles than reactant.