Trade on the Inca roads differed most strongly from trade on the Silk Road in which of the following ways?

Only food items were traded on the Inca roads, while only luxury goods were traded along the Silk Road.
The Inca roads crossed mountains, while the Silk Road traveled through lowlands.
Traders on Inca roads used horses to transport goods, while traders on the Silk Road used camels.
Trade along Inca roads was controlled by the government, while trade along the Silk Road was controlled by private merchants.