The Soviet Union disintegrated into fifteen separate countries in:
ADecember 1989
BDecember 1990
CNone of these
DDecember 1991
Correct answer
D. December 1991
Explanation
The Soviet Union officially dissolved on December 26, 1991, leading to the formation of 15 independent countries, including Russia, Ukraine, and others. The years 1989 and 1990 were significant for political changes in Eastern Europe and the USSR, but the formal disintegration occurred in 1991. Thus, “None of these” is incorrect.