GKFix MCQ Question

Which of the following is a heterogeneous equilibrium?

• A. CO(g) + H2O(g) ⇌ CO2(g) + H2(g)
• B. 2NOCl(g) ⇌ 2NO(g) + Cl2(g)
• C. Ca(OH)2(s) ⇌ Ca²⁺(aq) + 2OH⁻(aq)
• D. H2(g) + I2(g) ⇌ 2HI(g)