I believe it is B if im wrong forgive me.
The 1920s were a period of dramatic changes. More than half of all Americans now lived in cities and the growing affordability of the automobile made people more mobile than ever. Although the decade was known as the era of the Charleston dance craze, jazz, and flapper fashions, in many respects it was also quite conservative. At the same time as hemlines went up and moral values seemed to decline, the nation saw the end of its open immigration policy, the revival of the Ku Klux Klan, and the trial of a Tennessee high‐school teacher for teaching evolution.
I am not sure if this is the answer you are looking for but I gave it a try!!
I think because he says it would help them and give them more supplies.
The Federal government tried to stop slavery before the civil war by stopping its expansion into new territories and states in the west