Calcium chloride solution reacts with sodium carbonate solution

Reactions can occur because of a precipitation reaction

Double-Replacement reactions, happens if there is an ion exchange between two ion compounds in the reactant to form two new ion compounds in the product  

To predict whether this reaction can occur or not is one of them, the precipitation reaction. A precipitation reaction occurs if two ionic compounds which are dissolved reacted to produce one of the products of the ion compound does not dissolve. Formation of these precipitating compounds that cause reactions can occur  

Chloride solution reacts with Sodium carbonate solution

CaCl₂(aq)+Na₂CO₃(aq)⇒CaCO₃(s)+NaCl(aq)

Because Calcium carbonate, CaCO₃ an insoluble solid , it will precipitates so that a reaction can occur

i think it's letter a.