The correct option is D.
Oxygen has an atomic number of 8 and its configuration is 2, 6. For an atom to attain the octet structure it must have 8 electrons in its outermost shell, this implies that oxygen needs two more electrons to attain stability. In order to attain the octet structure, two oxygen atoms will donate two electrons each and share these electrons between themselves, thus, each atom will have 8 electrons in its outermost shell. This type of bond formation is called covalent bond.
