Answer: The Huang He River and the Yangtze River.
The Grand Canal is the longest and oldest canal or artificial river in the world. The oldest parts of the canal date back to the 5th century BC, but it was significantly rebuilt between 1271 and 1633. The canal starts at Beijing, passes through Tianjin, Hebei, Shandong, Jiangsu and Zhejiang to the city of Hangzhou. The canal links the Huang He and the Yangtze rivers.
D because cowboys ride horses not herds them and second they work on a ranch and I know that because I live on a ranch and herd cows
Because there would be more trade which will benefit the merchant.
Possible sickness. And multiple death situations.