What Is the Fundamental Difference Between Covalent and Ionic Bonding

What is the fundamental difference between covalent and ionic bonding?

A) In a covalent bond, the partners share a pair of electrons; in an ionic bond, one partner accepts electrons from the other.
B) In covalent bonding, both partners end up with filled outer electron shells; in ionic bonding, one partner does and the other does not.
C) Covalent bonding involves only the outermost electron shell; ionic bonding also involves the next electron shell inside the outermost shell.
D) Covalent bonds form between atoms of the same element; ionic bonds form between atoms of different elements.