Fully donating an electron results in an ionic bond, so A is the correct answer.
In comparison, B, a hydrogen bond, is a bond that forms between an H in one compound and an O, N, or F in another. It is among the strongest of intermolecular forces, while ionic/covalent bonds are intramolecular.
C, a covalent bond, is a bond that forms when atoms share electrons instead of donating them.
