Final answer:
The metal with a +2 oxidation state in the oxide is copper (Cu).
Step-by-step explanation:
The identity of the metal can be determined by considering the oxidation state of the metal in the oxide. The oxide contains 22.24% O by mass, which corresponds to an oxygen-to-metal ratio of 2:1. This suggests that the metal has a +2 oxidation state.
From the given options, the only metal with a +2 oxidation state is copper (Cu). Therefore, the correct answer is d. Cu.