The correct option is C m-nitroaniline > p-nitroaniline > o-nitroaniline
Nitro group is an electron-withdrawing group. It mainly withdraws electrons from the ortho and para positions by -M effect. Therefore para isomer is less basic than meta isomer.
Ortho substituted anilines are generally weaker bases than aniline irrespective of the electron releasing or electron- withdrawing nature of the substituent. This is due to ortho effect.
Hence decreasing order of basicity of the isomers of nitroaniline: m - nitroaniline > p - nitroaniline > o - nitroaniline
Hence, (c) is the correct option.