Final answer:
The oxygen atom in H2O is sp3 hybridized due to the tetrahedral arrangement of two lone pairs and two bonding pairs of electrons.
Step-by-step explanation:
The hybridization of the oxygen atom in H2O is sp3. This is because the molecular structure of water includes a tetrahedral arrangement with two lone pairs and two bonding pairs of electrons. These hybrid orbitals consist of one s orbital and three p orbitals mixing to form four sp3 hybrid orbitals, with two of the hybrid orbitals occupied by the lone pairs and the other two forming σ-bonds with hydrogen atoms.