What is the chemical formula of baking soda?

PYQ SSC JE (Junior Engineer) 2018

1. A.

   $\mathrm{Na_2CO_3.10H_2O}$

2. B.

   $\mathrm{Na_2CO_3}$

3. C.

   $\mathrm{NaHCO_3}$

4. D.

   NaOH

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