A is sodium. B is chlorine (atomic number 17). C is sodium chloride and D is sodium hydroxide.

2 Na  + Cl₂  → NaCl 

Electrolysis of sodium chloride can be given by following equation:

2NaCl +2 H₂O → 2NaOH + Cl₂ + H₂

When a carbonate ore is heated, we get carbon dioxide. A carbonate ore is calcinated to obtain oxide of the metal. Following equation shows calcinations of zinc carbonate.

ZnCO₃ +  ZnO  → CO₂

When a sulphide ore is roasted, we get Sulphur dioxide. Zinc sulphide is roasted to obtain zinc oxide.

2ZnS + 3O₂ → 2ZnO + 2SO₂

After any of the above steps; zinc oxide is reduced to obtain pure zinc.

ZnO + C → Zn +  CO