# The reaction of concentrated $\text{HNO}_3$ with $\text{Cu}$ or $\text{Ag}$ liberates
$\begin {array} {1 1} (A)\;\text{NO} & \quad (B)\;\text{NO}_2 \\ (C)\;\text{N}_2\text{O}_3 & \quad (D)\;\text{N}_2\text{O}_5 \end {array}$