Amongst baking soda, caustic soda and washing soda carbonate anion is present in:

We need to identify which among baking soda, caustic soda, and washing soda contains the carbonate anion (CO₃²⁻). Writing the chemical formulae, baking soda is NaHCO₃ (sodium bicarbonate) which contains the bicarbonate ion HCO₃⁻, not the carbonate ion. Caustic soda is NaOH (sodium hydroxide) containing the hydroxide ion OH⁻, and washing soda is Na₂CO₃·10H₂O (sodium carbonate decahydrate) which contains the carbonate ion CO₃²⁻.

Only washing soda contains the carbonate anion (CO₃²⁻). Note: baking soda contains bicarbonate (HCO₃⁻), which is different from carbonate (CO₃²⁻).

The answer is Option A: Washing Soda only.