The number of species from the following in which the central atom uses \( sp^3 \) hybrid orbitals in its bonding is ______. \( \text{NH}_3, \text{SO}_2, \text{SiO}_2, \text{BeCl}_2, \text{CO}_2, \text{H}_2\text{O}, \text{CH}_4, \text{BF}_3 \)
