Answer:
The correct answer is C. The event in the Soviet Union that involved the arrest of millions of Communist Party members, military officers, clergy, and intellectuals was the Great Purge.
Explanation:
The Great Purge was the name given to the series of campaigns of repression and political persecution carried out in the Soviet Union at the end of the 1930s. Hundreds of thousands of members of the Soviet Communist Party, socialists, anarchists and political opponents were persecuted or watched by the police; In addition, public trials were held, hundreds of thousands were sent to Gulag concentration camps and others were executed.
The Great Purge was crucial to consolidate Iosif Stalin's power. Although the Soviets later justified this bloody measure, arguing that the path of "saboteurs" or dissident elements for the future war with Nazi Germany was cleared, a large number of the victims were members of the Communist Party and leaders of the Armed Forces. The vast majority of these arrests were carried out by the Soviet secret police.