The inca used to move supplies on difficult mountain terrain.
a.
camels
b.
horses
c.
llamas
d.
oxen

C. Llamas
They were very useful to their economy as they were the source of course wool and fuel (from their dung).

C.  llamas

Explanation:

The llamas are domesticated south Americana animals that are used for the meat and the pack animals by the Andean culture since the pre-Colombian era and are well socialized.  And have been found in the Incas culture as they switched from a hunter-gather lifestyle to an agricultural society. Essential animal to carry the load in the difficult terrines.

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