The correct option is
C NH3>NF3>BF3In
NH3 and
NF3, the central nitrogen has three
σ bonds and one lone pair. Hence, both are
sp3 hybridized and posses trigonal pyramidal shape. In
BF3, the central boron has only three
σ bonds and so it is
sp2 hybridized and has trigonal planer shape.
In
BF3, the dipole moment vectors are arranged at
120∘. Therefore, the resultant of the two dipole moment vectors cancel out with the third dipole moment vector and hence
BF3 is non polar in nautre. In
NH3 and
NF3, the dipole moment vectors do not cancel out each other. Hence, both the molecules are polar in nature. In
NH3, the dipole moment vector of the bond and the lone pairs are in the same direction, while in
NF3, the dipole moment vector of the lone pair and the bond pairs are opposite in direction. Hence, the dipole moment of
NH3 is larger than
NF3.