A farmer living on the edge of a steep mountain would like to increase the amount of props he can grow. Which Inca advancement would have the most use for him?

The correct answer is a Terrace.

A farmer living on the edge of a steep mountain that would like to increase the number of crops he can grow, can build a terrace, one Inca advancement that could be of the most use for him.

The region of the Andes is a place where the tallest and difficult to access mountains exist. However, the Incas developed intelligent ways to harvest crops to take advantage of the steepest areas in the high mountains. They built terraces, cisterns and irrigation canals in the form of "s" or snakes in the slopes to angled down around the hills and mountains. The terraces covered thousands of hectares in ancient Peru, where Incas grew potatoes and corn.