| $$W$$ | $$X$$ | $$Y$$ | $$Z$$ | |
| (a) | $$CaO$$ | $$C{O_2}$$ | $$CaC{O_3}$$ | $$N{a_2}C{O_3}$$ |
| (b) | $$C{O_2}$$ | $$Ca{\left( {OH} \right)_2}$$ | $$Ca{\left( {HCO} \right)_3}$$ | $$NaHC{O_3}$$ |
| (c) | $$CaO$$ | $$C{O_2}$$ | $$Ca{\left( {OH} \right)_2}$$ | $$N{a_2}C{O_3}$$ |
| (d) | $$C{O_2}$$ | $$CaO$$ | $${H_2}C{O_3}$$ | $$N{a_2}C{O_3}$$ |