Which change would most likely have to take place first to encourage more human settlement in the outback a the climate would need to get warmer b the winters would need to be milder c the region would need more fertile land and water d people would need to build more cities there

The correct answer is D. The North has won the Civil War.

The entire poem by Whitman is actually an extended metaphor in which Captain represents Abraham Lincoln and the poem is about his death. He writes about how he's calling his captain to celebrate that they won the war but he finds that his captain has died, which refers to the assassination of Lincoln which happened quickly after the war ended.