The correct option is D NH3
∙ Electronegativity is the ability of an atom to attract the shared pair of electrons in a molecule.
∙ When atoms of elements with different electronegativities form a molecule, the atom with higher electronegativity attracts the shared pair of electrons towards itself as a result developing partial charges. These bonds are called polar covalent bond. Hence, NH3 is polar covalent compound
∙ N2, Cl2 and O2 are formed from the atoms of the same element. Since they have same electronegativities, they form non-polar molecules.