The formation of an ionic bond involves (1 point)transfer of electrons. transfer of neutrons. transfer of protons. sharing of electrons.

By definition, an ionic bond involves the transfer of electrons. The resulting charged particles are then electrostatically attracted to one another, which is what forms the bond. 

Transfer of neutrons and protons never takes place in a chemical reaction (you have to talk about nuclear reactions instead), and the sharing of electrons takes place in a covalent bond.

Answer = Transfer of electrons.

The teacher is mostly talking about the distillation of a mixture