Roasting of sulphides gives the gas X as a byproduct. This is colorless gas with choking smell of burnt sulphur and causes great damage to respiratory organs as a result of acid rain. Its aqueous solution is acidic, acts as a reducing agent and its acid has never been isolated. The gas X is -

Question

( A ) $H_2S$
( B ) $SO_3$
( C ) $CO_2$
( D ) $SO_2$