Need answers asap!! How were the Inca able to grow crops in the Andes mountains?

a
They built irrigation canals and terraces.
b
They used the rivers to water their crops.
c
They created floating gardens.
d
They used the land in the valleys.

Which of the following is an example of the pull factor known as economic migration? a. better educational opportunities pulling people towards a new country b. mexican laborers entering the us to work in agricultural jobs c. joining family members that are already in a new country d. crop failures driving people away from their country i am unsure on this question, i was thinking b? but i could be wrong.