What was the motivation for the exchange of commerce along the Silk Roads, Sea Roads, and Sand Roads?

A)
The acquisition of hard-to-find luxury items sustained trade along these
three exchange networks.
B)
Imposing cultural traditions on new people motived the exchange of
commerce along these three networks.
C)
The exchange of commerce along these three networks was motivated by
an opportunity to expand empires and take over new land.
D)
Exchange of commerce was influenced by similar climates along the three
networks. This allowed for easier exchange of goods and ideas.