Slavery was implicitly recognised in the original Constitution in provisions such as Article I, Section 2, Clause 3, commonly known as the Three-Fifths Compromise, which provided that three-fifths of each state's enslaved population (“other persons”) was to be added to its free population for the purposes of apportioning seats in the United States House of Representatives and direct taxes among the states.
E: both B and D. The automobile and the mass assembly line
