which molecule or compound below contains a polar covalent bond? why?

Question

C2H4

LiI

NCL3

ZnS

AgCl

Answer 1

Draw the Lewis dot structure for each of the molecules. You can eliminate LiI, ZnS and AgCl because they are not covalent (but they are polar). The correct one, of the two remaining, is the one with an unshared pair of electrons.