The statement that most accurately describes the political history of the Soviet Union after Stalin’s death is:
After Stalin’s death, the Soviet Union had very few instances of stability, as it went through multiple leaders. Most leaders only lasted for a couple of years, with the exception of Brezhnev.
This reflects the period of political instability characterized by a succession of short-lived leaders after Stalin, until Leonid Brezhnev established a more stable tenure that lasted for over a decade.