Remember that the polar covalent bond is determined if the electronegativity difference is between 0.4 and 1.7 and if the elements that are bonded are sharing their electrons unequally. For example, H has 1 electron and oxygen has 6 electrons of valence, so this would be a polar covalent bond because they're sharing unequally their electrons.
At first glance, you can see that if we have a bond with two oxygens, you can see that they would be sharing equally their electrons because they both have the same number of covalence electrons and this wouldn't be a polar covalent bond, it would call a nonpolar covalent bond, being this the answer: B. Oxygen.