Which Statement About the Red Scare After World War II

Which statement about the Red Scare after World War II is true?

A) Rooted in fears of a Soviet invasion, it essentially began as a reaction to revelations that the Russians had the bomb.
B) The administration, the House of Representatives, and the Senate all conducted probes of possible subversive activity.
C) With Truman's blessing, the McCarran Act of 1950 was passed, requiring all Communists to register with the attorney General.
D) American fears of Communist subversion eased once the Truman administration set up an internal loyalty program.