The correct answer is the Committee of Public Information.
The organization that specifically promoted support for the war among American people was the Committee of Public Information (CPI).
As a United States agency, the Committee of Public Information was established on April 13, 1917. The Committee was led by George Creel. The aim of the Committee was to provide information and propaganda to the American People during World War 1, in order to get the support of the American citizens for the war effort.
The other options of the question were, b) the Red Cross, c) the Council of National Defense, and d) the War Industry Board.