Which of the following countries did not join the Commonwealth of Independent States (CIS) in December 1991?

Hungary

The correct answer is Option 4 - Hungary

Russia, Belarus, Ukraine, Armenia, Azerbaijan, Moldova, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan joined the CIS in December 1991. Hungary was not among these countries.

1991 December: Russia, Belarus and Ukraine decide to annul the 1922 Treaty on the Creation of the USSR and establish the Commonwealth of Independent States (CIS); Armenia, Azerbaijan, Moldova, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan join the CIS (Georgia joins later in 1993); Russia takes over the USSR seat in the United Nations.

In December 1991, under the leadership of Yeltsin, Russia, Ukraine and Belarus, three major republics of the USSR, declared that the Soviet Union was disbanded. The Communist Party of the Soviet Union was banned. Capitalism and democracy were adopted as the bases for the post-Soviet republics. The declaration on the disintegration of the USSR and the formation of the Commonwealth of Independent States (CIS) came as a surprise to the other republics, especially to the Central Asian ones. The exclusion of these republics was an issue that was quickly solved by making them founding members of the CIS.

More about CIS:

The Commonwealth of Independent States (CIS) is a regional intergovernmental organization in Eurasia. As the Soviet Union disintegrated in 1991, Belarus, Russia, and Ukraine signed the Belovezha Accords on 8 December 1991, declaring that the Union had effectively ceased to exist and proclaimed the CIS in its place. The CIS promotes economic, political, and military cooperation between the member states.