Sodium salt of an organic acid ‘X’ produces effervescence with conc. $H_2SO_4$. ‘X’ reacts with the acidified aqueous $CaCl_2$ solution to give a white precipitate which decolourises acidic solution of $KMnO_4$ ‘X’ is :

Question

$\begin{array}{1 1} (1)CH_3COONa \\ (2) Na_2C_2O_4 \\ (3) C_6H_5COONa \\ (4) HCOONa \end{array} $