Why did the government support homesteading

In 1860, a homestead bill providing Federal land grants to western settlers was passed by Congress only to be vetoed by President Buchanan. With the secession of Southern states from the Union and therefore removal of the slavery issue, finally, in 1862, the Homestead Act was passed and signed into law

The answer choices were:

Explanation:

A. to encourage settlers to farm the western land

B. to encourage railroad companies

C. to put down tracks to expand travel on the Mississippi River

D. to encourage trade with Canada

Can someone tell me which one?