c
\(\mathrm{CO}_{2}\) and \(\mathrm{CH}_{4}\) have zero dipole moment as these are symmetrical in nature.

Between \(N H_{3}\) and \(N F_{3}, N F_{3}\) has greater dipole mough in \(N H_{3}\) and \(N F_{3}\) both, \(N\) possesses one lone pair of electrons.

This is because in case of \(N H_{3},\) the net \(N\) - \(H\) bond dipole is in the same direction as the direction of dipole of lone pair but in case of \(N F_{3},\) the direction of net bond dipole of three- \(N-F\) bonds is opposite than that of the dipole of the then lone pair.