The answer is D: hydrogen bonds. Let's look at each choice in turn. Covalent bonds are present within a water molecule, but two adjacent water molecules will share no covalent bonds between the two of them. So A is wrong. Water involves only hydrogen and oxygen. There are no metals present so B is wrong. Water is a covalent molecule. There are no ions or ionic bonds present in pure water itself so C is wrong. Van der Waals forces are general intermolecular forces of attraction between molecules. They could be present in water but they are very weak intermolecular forces. Hydrogen bonds are much stronger intermolecular bonds. The hydrogen on a water molecule will form a hydrogen bond with an oxygen atom on an adjacent molecule due to their difference in electronegativity. So D is the better answer here than E.