In the given reaction cycle

X, Y and Z respectively are

### Explanation

Mixing aqueous $$CaCl_2$$ and $$Na_2CO_3$$ results in a double displacement (precipitation) reaction.

$$CaCl_2(aq)+Na_2CO_3(aq)\rightarrow CaCO_3(s)\downarrow+2NaCl(aq)$$

Thus, the products formed are calcium carbonate and sodium chloride.

Hence,

$$X=CaCO_3$$

$$Y=NaCl$$

To convert $$CaCO_3$$ back into $$CaCl_2$$, it is treated with hydrochloric acid.

$$CaCO_3(s)+2HCl(aq)\rightarrow CaCl_2(aq)+H_2O(l)+CO_2(g)$$

Therefore,

$$Z=HCl$$

Hence, the correct matching is

$$X=CaCO_3,\quad Y=NaCl,\quad Z=HCl$$

This corresponds to Option B