The correct option is C N - F
Polarity of the bond depends upon the electronegativity difference of the two atoms forming the bond. Greater the electronegativity difference, more is the polarity of the bond.
N - Cl O - F N - F N - N
3.0 - 3.0 3.5 - 4.0 3.0 - 4.0 3.0 - 3.0