Which of the following city names in the Soviet Union was used during the Communist period?

During the Communist period in the Soviet Union, Leningrad was the name given to the city formerly known as St. Petersburg. The name change occurred in 1924 to honor Vladimir Lenin after his death. This designation reflected the ideology of the time, where cities were often renamed in favor of prominent Communist figures or principles. Though the city’s name was reverted back to St. Petersburg after the fall of the Soviet Union in 1991, during the Communist era, Leningrad was significant not only as a major cultural and industrial center but also for its historical importance.

Moscow remained unchanged during this period, Stalingrad was renamed Volgograd after Stalin's death as part of a de-Stalinization process, and Volgograd is the present-day name of that city. Therefore, Leningrad is the correct answer as it specifically references the city's name during the Communist period.