What gave portugal an advantage in the slave trade?

Which best describes the purpose of the south carolina exposition and protest, which was written by john c. calhoun? a) to explain why the south was nullifying the tariff of 1828 b) to describe the ways the tariff of 1828 would southerners c) to persuade northern states to rebel against the federal government d) to ask england for if the south decided to secede from the union