One of the most interesting places in Yangzhou are often visited by foreigners is the Wes

问题补充：

One of the most interesting places in Yangzhou are often visited by foreigners is the West Slender Lake.

A. what

B. who

C. that

D. /

答案：

A. what

B. who

(答案→)C. that

D. /

解析：定语从句。根据句意：被外国旅游者参观的最著名的地方是西湖。Are often visited by foreigners修饰先行词places。