The correct answer is C. Aragonite and Conchiolin.
Aragonite is a form of calcium carbonate that is found in pearls. It is a white, rhombohedral mineral that is the main component of the shells of mollusks, including oysters. Conchiolin is a protein that is found in the shells of mollusks. It is a brown, fibrous material that is responsible for the color and luster of pearls.
Option A is incorrect because calcium oxide is not a constituent of pearls. Calcium oxide is a white, powdery substance that is used in the manufacture of cement and other building materials.
Option B is incorrect because magnesium carbonate is not a constituent of pearls. Magnesium carbonate is a white, crystalline mineral that is used in the manufacture of fertilizers and other chemicals.
Option D is incorrect because ammonium sulfate and sodium carbonate are not constituents of pearls. Ammonium sulfate is a white, crystalline salt that is used in the manufacture of fertilizers and other chemicals. Sodium carbonate is a white, crystalline salt that is used in the manufacture of soap and other cleaning products.