(A) Magnesium hydroxide Mg(OH)2 is used as a constituent of sorrel cement.
(B) Barium sulphate BaSO4 is used as a constituent of lithopone.
(C) Magnesium sulphate MgSO4 is used as purgative in medicine.
(D) Calcium cyanide Ca(CN)2 is used as a fertilizer.