Answer: Hydrogen bonds.
Step-by-step explanation:
A water molecule is composed of two hydrogen atoms and one oxygen atom, with a partially positive hydrogen atom covalently bonded to a more electronegative oxygen atom. Water molecules are polar due to oxygen atoms having a greater electronegativity value (easier for oxygen than hydrogen to attract a pair of electrons) and this results in unequal partial charges. The polarity in a hydrogen atom of one water molecule attracts the oxygen atom of another water molecule, which results in the formation of hydrogen bonds between water molecules.