$$\begin{gathered} \mathrm{Cu}+\text{ conc. }{\mathrm{HNO}}_3⟶\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2+\mathrm{X} \\ \left(\mathrm{bot}\right) \end{gathered}$$ 

(oxide of nitrogen); then X is :

In terms of the reaction involving concentrated nitric acid and copper, copper is oxidized to yield $C{u}^{2+}$ions. Nitric acid is converted into nitrogen dioxide, a deadly dark gas with an unpleasant odour. Additionally, the process produces cupric nitrate, $Cu(N{O}_3{)}_2$

$\mathrm{Cu}+\mathrm{conc}\cdot \mathrm{HNO}\to \mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2+{\mathrm{NO}}_2$

Hence, option B is the correct answer.