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

The story behind the answer

Afghanistan is correct because it was never a Soviet republic. Turkmenistan, Kazakhstan, and Uzbekistan were all constituent republics of the USSR from the 1920s until the Soviet Union dissolved in 1991. Although the Soviet Union invaded Afghanistan in 1979 and fought there until 1989, Afghanistan remained an independent country and was never annexed.

Context tip: Think “the five ex‑Soviet -stans” in Central Asia—Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. Afghanistan (and Pakistan) sit next door but were never part of the USSR. A memory aid: “Five Soviet -stans, but never Af- or Pa-kistan.”