—Look! The boy is running so fast!—It’s hard to that his right leg was once broken.A.warn

问题补充：

—Look! The boy is running so fast!

—It’s hard to that his right leg was once broken.

A.warn B.find C.imagine

答案：

解析：此题重点考查三个单词含义的区别，warn警告，提醒；find找到，发现；imagine想象。句意：看，这个男孩跑的如此快。——很难想象他的右腿受过伤。根据语境可知只有C符合题意。