GKFix MCQ Question

What is the correct expression for Kp for the reaction CaCO3(s) ⇌ CaO(s) + CO2(g)?

• A. Kp = pCaCO₃
• B. Kp = pCaO / pCaCO₃
• C. Kp = pCO₂
• D. Kp = pCaO × pCO₂ / pCaCO₃