Which of the following molecules is polar?

A

BH3​

B

NF3​

C

C2​H6​

D

SF6​

E

CCl4​

Three electrons of Nitrogen are involved in bond formation with three Fluorine atoms. Still, two electrons remain as a lone pair on Nitrogen atom. Thus, this lone pair repels the bond pair and the structure of Nitrogen trifluoride is assymmetric in nature. It is pyramidal in shape.

Because of the presence of the lone pair above Nitrogen atom, and this shape, NF3​ is a polar molecule.

Option B is the correct answer.