Which pair of elements in the diagram is most likely to form a covalent bond?

This question is incomplete

Explanation:

This question is incomplete. A covalent bond is a bond that involves the sharing of valence electrons (shared pair) by two atoms of the same/different elements/compounds. The electrons (valence) that are involved in covalent bonding are not the ones in pairs (lone pairs) on the outermost shell of the atom. For example, the single electron on a hydrogen atom is shared with another hydrogen to form hydrogen gas (H₂).

Another example is when the two individual/unpaired electrons on the outermost shell of an oxygen atom binds with two other unpaired electrons on the outermost shell of another oxygen atom.

Another example is when two different electrons from two hydrogen atom binds singly with the two unpaired electrons on the outermost shell of an oxygen atom to form water.

The diagram in the attachment provides illustration on the examples given.

it means there are 3 atoms of oxygen