An element was burnt in limited supply of oxygen . The oxide (H) was formed which was treated with water to yield an acid (B). The acid (B) was oxidised to give another acid (C). The acid (C) gave yellow precipitate with $AgNO_3$ solution . The oxide (A) is

Question

$\begin{array}{1 1} SO_2 \\ NO_2 \\ P_4O_6 \\ SO_3 \end{array} $