Which of these conclusions is supported by the voyages of both hsin t'ang shu and marco polo?
a) countries prefer to fight wars against one another before accepting a trade relationship.
b) long-distance trade exposes people to previously unknown ideas, peoples, and cultures
c)despite the efforts of chinese and europeans, islam quickly spread along the silk road.
d)the silk road was excellent for transporting gold but collapsed when new product were introduced.