Final answer:
The House Committee on Un-American Activities (HUAC) was responsible for investigating domestic communism during the second Red Scare.
Step-by-step explanation:
The committee that investigated instances of domestic communism during the second Red Scare was the House Committee on Un-American Activities (HUAC).
Throughout the late 1940s and 1950s, HUAC conducted numerous investigations into alleged communist influence and subversive activities within the United States. This included high-profile inquiries into industries such as the Hollywood film industry, which brought considerable attention and notoriety to the committee.
Witnesses before HUAC were subpoenaed and compelled to testify about their own and others' political associations, and the consequences of the hearings often included blacklisting and loss of employment, particularly for those in the entertainment industry.