Final answer:
The formulas for calcium sulfide, potassium chloride, and barium bromide are CaS, KCl, and BaBr₂ respectively, resulting from the neutral combination of their respective ions.
Step-by-step explanation:
The formula for various ionic compounds can be derived from the charges of the constituent ions, and proper crisscrossing and simplification of those charges to ensure the overall neutrality of the compound. Given three ionic compounds, we can find their formulas:
Therefore, the correct formulas for the given compounds are CaS for calcium sulfide, KCl for potassium chloride, and BaBr2 for barium bromide, which corresponds to option (a).