Which one of the following countries is NOT a member of the United Nations Organisation?

Correct option is D

The correct answer is (d) Taiwan
Explanation:
· Taiwan (Republic of China) is not a member of the United Nations.
· Taiwan was a founding member of the UN, but in 1971, the UN General Assembly passed Resolution 2758, which recognized the People's Republic of China (PRC) as the only legitimate representative of China.
· Since then, the PRC has held China's seat, including the permanent seat on the Security Council.
Information Booster:
· Sudan, Yemen, and Serbia are all full member states of the UN.
· Vatican City and Palestine hold "Non-member Observer State" status.