How did nomads in Asia and the Middle East impact Silk Road trade? A. Controlled silk production

B. Controlled gold and salt mines

C. Connected other groups without direction interaction

D. Isolated civilizations from each other other

One drawback of voluntary trade is that it a.requires two groups to use a common language b.can make one group dependent upon another for necessary goods c.doesn't occur unless there is a shortage of goods for at least one group d.forces groups to rely on themselves to produce all the goods they need