He criticized the Catholic church for not allowing the people to teach our question the clergy. He also criticized the belief that if people didn't accept the Pope as the head of the church they would go to Hell.
The colonies (13) would first pick up Africans from Africa, then travel back to the US to keep some for their own and then trade them to Europe. This is also known as the Triangular Slave Trade. If you are to look on a map, you can see that from Africa, to the US, then to Europe, it forms a triangle.
The Constitutional Convention took place from May 14 to September 17, 1787, in Philadelphia, Pennsylvania.