Final answer:
CaCO₃ (a) will precipitate.
Step-by-step explanation:
If Na₂CO₃ and CaCl₂ are both dissolved into the same solution, CaCO₃ (a) will precipitate. According to the solubility rules, all carbonates, except for those of potassium, sodium, and ammonium, are insoluble. CaCO₃ is an example of an insoluble carbonate, so it will form a precipitate when Na₂CO₃ and CaCl₂ are dissolved together.