question: What two systems were compare in the Soviet Union in 1970 ?
answer: 3 kV DC and 25 kV AC ( 50 Hz
turker_answer: The two systems that were compared in the Soviet Union in 1970 is 3 kV DC and 25 kV AC ( 50 Hz ) .
rule-based: 3 kV DC and 25 kV AC ( 50 Hz were compare in the Soviet Union in 1970 .