Which phenomenon did triangular trade most directly encourage? 

The phenomenon that triangular trade most directly encouraged was slavery. The first part of the triangle was the crossing of the Atlantic Ocean by Europeans wishing to sell their products. With the money obtained the europeans would buy slaves; sometimes they would just trade the products they brought directly for slaves. The same european ships would then sail to America to sell the slaves as plantation labourers. With the money obtained the europeans bought raw products like cotton and took them to Europe for further processing. The complete cycle took like a year.

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