Question 8
What decides whether a covalent bond is polar or non-polar?
The right answer is the one marked above.
The difference in electronegativity between the two atoms. Where there is no difference the electrons sit symmetrically and the bond is non-polar; where there is one, they are pulled to one side.
N2 shows that the number of shared pairs is irrelevant — it has three and is still non-polar. Bond strength and molecule size are different properties again.