D. How slaves would be counted for the purposes of representation in Congress.
Explanation:
The Three-Fifths Compromise was implemented by state representatives during the Constitutional Convention of 1787 in America. The way in which slaves would be calculated in order to define the whole population of a state was crucial, since this result would be used to establish the amount of seats that would belong to that state in the House of Representatives during the following 10 years. So, under this compromise, three out of five slaves were considered as people.
