Why did people travel in caravans between Egypt and Mesopotamia to China?

Which of the following statements about imprisonment rates in the united states is true? the united states imprisons people at a higher rate than russia, mexico, or canada. the united states imprisons people at a lower rate than russia or south africa, but higher than israel. the united states imprisons people at a lower rate than russia, mexico, or canada. russia, south africa, and mexico each imprison more people than the united states.