The Great Wall is wall in the world. There are many stories about it. A. long B. longer C

问题补充：

The Great Wall is wall in the world. There are many stories about it.

A. long

B. longer

C. the longest

D. the long

答案：

A. long

B. longer

(答案→)C. the longest

D. the long

解析：句意：长城是世界上最长的城墙。有许多关于它的故事。结合语境可知本句表示在多个中进行对比，故用形容词的最高级，选C。