What substance does the liver change into urea?

Which of the following answers best describe why the fugitive slave act was so controversial? a fugitive slaves who were caught were to be sent back to africa, and southern states disagreed with this practice. b it required all runaway slaves to be sentenced to death, and most people were against this extreme form of punishment. c fugitive slaves were required to work twice as long before they could be freed, and northern states opposed this. d it required all americans to return runaway slaves to their owners, and abolitionists in free states opposed this law.