In which equilibrium are both equilibrium constants $K_c$ and $K_p$ unitless?
- A$\text{H}_2(g) + \text{I}_2(g) \rightleftharpoons 2\text{HI}(g)$
- B$\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$
- C$\text{N}_2\text{O}_4(g) \rightleftharpoons 2\text{NO}_2(g)$
- D$\text{SO}_2(g) + \frac{1}{2}\text{O}_2(g) \rightleftharpoons \text{SO}_3(g)$