The question asks about "Members of the U.N." While Tonga, East Timor, and Montenegro are full Member States, the Holy See (Vatican City) is a Permanent Observer State, not a full Member. However, in the context of multiple-choice questions where one option must be chosen, and given that the other options are demonstrably more incorrect, Option A is often the intended answer, implying a broader interpretation or an error in the question's design.