which former soviet republic was part of the u.s.s.r?\nbulgaria\nromania\nukraine\nserbia

which former soviet republic was part of the u.s.s.r?\nbulgaria\nromania\nukraine\nserbia
Answer
Brief Explanations:
Bulgaria, Romania, and Serbia were never part of the Soviet Union. Ukraine was one of the 15 Soviet Socialist Republics that made up the USSR.
Answer:
Ukraine