In terms of bonding, which type has complete electron sharing?

The correct choice focuses on the nature of electron sharing in a nonpolar covalent bond. In a nonpolar covalent bond, two atoms share a pair of electrons equally because they have similar electronegativities. This equality in sharing means that neither atom has a stronger pull on the shared electrons compared to the other, resulting in a balanced charge distribution.

This complete sharing leads to the formation of a stable bond while also reflecting symmetrical molecular geometry. Common examples of nonpolar covalent bonds include diatomic molecules like nitrogen (N2) and oxygen (O2), where the identical atoms share their electrons equally due to possessing the same electronegativity.

By contrast, in polar covalent bonds, the sharing is unequal due to a significant difference in electronegativity between the bonded atoms, resulting in partial positive and negative charges. Ionic bonds involve the transfer of electrons from one atom to another, leading to the formation of charged ions rather than sharing. Metallic bonds are characterized by a 'sea of electrons' that are delocalized among a lattice of metal cations, which is a different type of bonding from electron sharing. Thus, the nonpolar covalent bond represents a scenario of complete and equal electron sharing.