11. THE P-BLOCK ELEMENTS
Explanation:
Boron has three valence electrons, so it is supposed to make bonds in a molecule with hybridization, as only s and two orbitals are used in hybridization and last orbitalis vacant.
But diborane, contains two electrons each, three centred bonds. Each Boron atom is in a link with four hydrogen atoms. This makes tetrahedral geometry.
Hence, each Boron atom is - hybridized.