Concept:A coordinate bond (dative bond) is formed when a shared pair of electrons comes entirely from one atom.Explanation:In an ordinary covalent bond, each atom supplies one electron to form the shared pair.In a dative bond, one atom donates both electrons of the shared pair while the other atom accepts them.This bonding is also called a coordinate covalent bond.Thus, the bond described in the question is a dative bond.Answer:B. dative