Which statement about covalent bonds is true?

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Covalent bonding hinges on sharing electrons to reach a more stable arrangement. There is an optimal separation between the nuclei—the internuclear distance—where the overall energy is minimized. At this bond length, the attraction between each nucleus and the shared electrons lowers energy, while repulsions between electrons and between the two nuclei prevent collapse. This balance gives the bond its characteristic length and strength, so forming at that preferred distance is how covalent bonds are most stable.

This helps explain why the other statements aren’t true. Transferring electrons to create ions describes ionic bonds, not covalent ones. Complete delocalization of all electrons isn’t a general feature of covalent bonds (it occurs in metals or in certain resonance systems, but not for typical covalent bonds). And covalent bonds do depend on distance—too far apart they don’t interact to form a bond, and too close they experience strong repulsion, so there is a specific bond length where the bond is favored.