Which tactic did george creel, the head of the committee on public information, use to gain the support of us citizens for the war?

A. He promised job opportunists in the US military for African Americans from southern states

Correct  He promoted anti-German and pro-war propaganda through posters, movies, and booklets.

Detail:

George Creel was appointed as head of the Committee of Public Information by President Woodrow Wilson.  Pres. Wilson created the committee by issuing Executive Order 2594 on April 13, 1917, just a week after the United States had declared war against Germany and entered into The Great War (which we now know as World War I).  

I've attached a sample image of one such "anti-German and pro-war propaganda" posters produced by the Committee of Public Information.

Creel's committee used not only posters, movies and books, but also leaflets, press releases and billboards.  It was a multi-media campaign. They even had 75,000 speakers who volunteered to be "Four Minute Men," giving 4-minute patriotic speeches at schools and public events.

sorry just needed 5 points