Final answer:
The House Committee on Un-American Activities (HUAC) was responsible for investigating threats of communist infiltration in the United States, including in Hollywood.
Step-by-step explanation:
The House Committee on Un-American Activities (HUAC) was responsible for investigating threats of communist infiltration in the United States, including in Hollywood. Originally created as a congressional committee to search out disloyalty prior to WWII, HUAC gained national attention in 1947 when it began investigating Communist influence in the movie industry.
The committee held hearings and summoned witnesses, including actors, directors, writers, and other professionals in the entertainment industry, to testify about their political beliefs and associations. Witnesses were subpoenaed and required to testify before the committee, and those who refused often lost their jobs and found themselves on a blacklist, which prevented them from securing employment.