The correct answer is: A. Belarus and Ukraine
Belarus and Ukraine were integral parts of the USSR and not independent countries, but had separate UN memberships.
Belarus was a founding member of the USSR in 1922, and Ukraine joined in 1922. Both countries were constituent republics of the USSR, and they had their own governments and parliaments. However, they were not independent countries, and they were subject to the authority of the Soviet government in Moscow.
Belarus and Ukraine were both members of the United Nations from 1945. However, their membership was not as independent countries, but as constituent republics of the USSR. This meant that the Soviet Union was the only country that could represent Belarus and Ukraine in the UN.
In December 1991, Belarus and Ukraine declared their independence from the USSR. They became independent countries, and they were admitted to the UN as independent members.
The other options are incorrect because they are not constituent republics of the USSR.
- Czech Republic and Slovakia were constituent republics of Czechoslovakia, which was not a member of the USSR.
- Tonga and Nauru are independent countries that were never part of the USSR.