# Sodium thiosulphate reacts with $dil\: HCI$ to form $NaCI,H_2O, \underline X\: and \: \underline Y.\: \underline X$ reacts with $Na_2S$ to form $Na_2S_2O_3$ and $\underline Y$ . Which one of the following is $\underline Y$.

$\begin {array} {1 1} (1)\;H_2S & \quad (2)\;SO_2 \\ (3)\;H_2SO_4 & \quad (4)\;S \end {array}$

(4) S