What was the significance/importance of the Thirteenth, Fourteenth, and Fifteenth Amendments getting passed at the conclusion of the Civil War

According to the qianlong emperor, why was china not interested in importing anything else?

Which of the following inventions most directly allowed ancient farmers to produce a surplus ?

Which of these marketing methods henry ford sell the model t to many people who had never before owned a car? a) offering free maintenance on cars for a full year b) airing television commercials with memorable slogans c) advertising with the new communication outlets such as radio d) offering many different colors and models for buyers to choose from