Which of these countries was NOT a part of the Soviet Union?

Afghanistan was not a part of the Soviet Union. Although several Central and Eastern European countries, such as Lithuania, Latvia, Estonia, Ukraine, Belarus, and Moldova, were part of the Soviet Union during the majority of the 20th century, Afghanistan was never incorporated into the Soviet Union. However, it did experience a period of Soviet military intervention in the late 1970s and throughout the 1980s during the Soviet-Afghan War, as the Soviet Union sought to support a communist government in Afghanistan.