which type of bonding involves the complete transfer of a valence electron from a less electronegative atom…

Brief Explanations:

Ionic bonding occurs when there is a complete transfer of a valence - electron from a less electronegative atom to a more electronegative atom, forming ions that are held together by electrostatic forces. Metallic bonding involves a sea of delocalized electrons among metal atoms. Covalent bonding is the sharing of electrons between atoms. Hydrogen bonding is a special type of dipole - dipole interaction involving hydrogen and a highly electronegative atom.

Answer:

A. Ionic bonding