The silk routes were important in ancient times because they
(a) facilitated the exchange of goods and ideas between
china and the roman empire
(b) allowed gold and silver mined in china to be traded for
european furs and wool cloth
(c) provided trade links between the people of siberia and
the people living on islands in the bering sea
(d) provided a conduit for trade in silk, porcelain, and costly
gems between china and japan
(e) allowed carts and carriages to travel on paved roads
across northern asia as far west as the caspian sea