The Trade Conducted Along the Silk Roads Was Largely a Relay

The trade conducted along the Silk Roads was largely a relay trade because

A) it linked the entire world into a single trade network.
B) it linked the civilizations of coastal Eurasia but bypassed the pastoral peoples of the interior.
C) goods were passed down the line rather than carried by one merchant along the entire route.
D) it sustained the long-distance trade in the Americas.