Answer:
B. Deserts
E. Mountains
Step-by-step explanation:
The silk road is the term that's commonly used to described land routes that connected Europe, Asia, and Africa. Merchants between 2nd - 14th century used this route to distribute their goods.
Deserts and mountains always considered as a massive hindrance for the traders during that time.
Not many people/animals can live through the Desert. Most of the successful caravans use Camels instead of horses, making the transportation became really slow. Since the people haven't developed an aviation technology in this time period, reaching areas on top of the mountains was also very difficult.