‘X’ is a salt which on thermal decomposition gives an acidic oxide and a basic oxide. ‘X’ imparts no colour to the oxidizing flame of Bunsen burner. ‘X’ is

• A

  ${\mathrm{CaCO}}_3$

• B

  ${\mathrm{MgCO}}_3$

• C

  $\mathrm{NaCl}$

• D

  ${\mathrm{KNO}}_3$