O CaClâ‚‚
Explanation:
The compound most likely to contain an ionic bond is CaClâ‚‚ because it is the only specie with a metal and non-metal.
The metal here is Ca and non-metal is Cl.
In this bond type, there is a transfer of electrons from the metal to the non-metal. There must be a significant electronegativity difference between the two bodies for this bond to form. The metal Calcium loses two electrons and becomes isoelectronic with argon. Two chlorine non-metal gain one of the electrons each and becomes stable. The electrostatic attraction between the oppositely charged ions results in the ionic bonding.