Correct Answer - C
In nitration of aromatic nucleus, the attraking species is an electrophile, i.e. nitronium ion `(NO_(2)^(+))`. It is obtained by the reaction of conc. `HNO_(3)` and `H_(2)SO_(4)`.
`H_(2)SO_(4)+HNO_(3)rarr H_(2)O+HSO_(4)^(-)+NO_(2)^(+)`