Final answer:
Covalent bonding involves the sharing of electrons between atoms, which can be equal or unequal depending on the atoms involved, leading to nonpolar or polar covalent bonds, respectively.
Step-by-step explanation:
During covalent bonding, option C is correct: electrons are shared between atoms. Unlike ionic bonding, where electrons are transferred to achieve filled outer electron shells and ions are formed, covalent bonding involves the mutual sharing of electrons to fill the valence shell of each atom involved. This leads to the formation of molecules with shared electron pairs, creating covalent bonds. Examples of this can be seen in diatomic molecules like O₂, where two oxygen atoms share electrons equally, or in molecules like H₂O, where the shared electrons are more attracted to the oxygen atom, resulting in a polar covalent bond.