The correct formula unit for cupric oxide (also known as copper(II) oxide) consists of 1 Cu²⁺ ion and 1 O²⁻ ion.
The cupric (Cu²⁺) indicates that copper has a +2 oxidation state, and oxide (O²⁻) indicates that oxygen has a -2 oxidation state. To achieve charge neutrality in the compound, one Cu²⁺ ion combines with one O²⁻ ion, resulting in the formula CuO.
Thus, the correct response is: 1 Cu²⁺ ion and 1 O²⁻ ion.