Which of the following would you expect to have polar covalent bonds?
A) MgF2
B) N2
C) F2
D) NF3
E) NaF

Okay, we can cancel MgF2 and NaF right away because they have bonds between metals and nonmetals, which are ionic and not covalent

N2 and F2 are both diatomic molecules where both atoms are the same, and thus they will not be polar

NF3 is the only choice left, and this makes sense because the nitrogen will have a lone pair of electrons forming one "corner" of its tetrahedral shape, causing it to be polar