Answer:
A. More people moved to the cities in the Middle East to be near ports.
Explanation:
To trade long distance, medieval merchants had three routes: land, river and sea. Although land transport allowed to reach inland areas without rivers, it was always the most expensive and painful, since the roads were bad and unsafe and a large amount of taxes had to be paid.
For safety, merchants preferred river transportation. The most important river networks were those of the Po River, the Rhone, the lattice of rivers in the Flanders area. the Rhine and the Danube. However, the river environment was also subject to taxes.
The cheapest means of transport was the sea, so it was preferred despite the risks of shipwreck and piracy, the low capacity of the ships and the slow travel. In addition, a single ship could carry the loads of several merchants at once.
