A community in this South American nation was settled by Confederate refugees after the Civil War since this nation still had legalized slavery. The area where this nation is now located was explored by Portuguese captain Pedro Cabral, requiring a change to the Treaty of Tordesillas. Two former leaders of this nation, Lula da Silva and Dilma Rousseff, are currently serving prison terms. For 10 points, name this largest South American nation, currently led by Michel Temer.
a) Argentina
b) Colombia
c) Brazil
d) Venezuela