Which of the following best explains Niebuhr's sense of alarm about Soviet intentions in occupied Eastern Europe?
a) Niebuhr believed in the Soviet Union's commitment to fostering democratic values in Eastern Europe.
b) Niebuhr was concerned about the potential spread of communism and the suppression of democratic principles by the Soviet Union.
c) Niebuhr was confident in the Soviet Union's peaceful coexistence with Western nations and its respect for territorial sovereignty.
d) Niebuhr believed that the Soviet Union's actions in Eastern Europe were driven by a desire for economic cooperation and mutual benefit.