Refer to the image.
A drawing of Elmina Castle in Ghana in 1660. A large castle sits on a peninsula. Smaller homes are behind the castle. Small ships are in the water.
A view of the Portuguese-built Elmina Castle in Ghana, ca. 1660
Which of the following innovations contributed most directly to the establishment of European trading posts such as the one depicted in the image?
Gunpowder
Caravel ships
Cartography
Steam engine