# $NO_2$ combines with atmospheric moisture to form mixture of $2NO_2+H_2O\rightarrow y + HNO_3$.The y is

$\begin{array}{1 1}(a)\;HNO_2\\(b)\;HNO\\(c)\;HNO_4\\(d)\;NO_2\end{array}$

$2NO_2+H_2O\rightarrow HNO_3+HNO_2$
Hence y is $HNO_2$
Hence (a) is the correct answer.