The correct answer is D. Propaganda.
Explanation
During the mandate of the Soviet Union, propaganda was a tool of massive persuasion of the Marxist-Leninist ideology. For example, during the government of Joseph Stalin, posters were used to positively promote his works and policies and to convince the population that he was the best ruler. However, it was a way of hiding his bad deeds like compulsory labor camps. Therefore, the correct answer is D. Propaganda.
