following balanced chemical

Question

reaction:
Ca2+
(aq)+ CO3
2--
(aq) ⇄CaCO3(S)
The amount of dissolved CaCO3 can be
increased on adding:
CaCO3(S)
KNO3(S)
Na2CO3(S)
CH3COOH(S)

Answer 1

For every action there is an opposite and equal reaction.

By adding Na2CO3 that will give you the CO3 which will push the reaction to form more CaCO3