The formula of baking soda is:

Correct answer: (d) NaHCO3

Explanation

Baking soda is chemically sodium bicarbonate (NaHCO₃), a mild base used in cooking and cleaning.

On heating or reacting with acid it releases carbon dioxide (CO₂), which makes dough rise.

Distractors: Na₂CO₃ is washing soda, K₂CO₃ is potassium carbonate, and KHCO₃ is potassium bicarbonate.