Electrophilic substitution of benzene with conc. HNO₃ and HNO₂
Nitrosyl cation, $\ce{NO^+}$, is a better electrophile than molecular $\ce{HNO3}$ (you don't get $\ce{NO_2^+}$ in this system without sulfuric acid or other strong auxiliary acid) and so you get nitrosobenzene in the substitution reaction.  But then the nitrosyl group with its nonbonding electron pair is an attractive target for oxidation by the nitric acid and thereby is converted to $\ce{NO_2}$.  Thus nitrobenzene.  Then, the nitrobenzene, deactivated by the nitro group, will not react with the relatively mild electrophile $\ce{NO^+}$ anymore, meaning products C and D are never reached (and their nitrosyl groups would not have survived anyway).