—Look! He’s running so fast!—Hard to his legs were once broken. A. know B. imagine C. real

问题补充：

—Look! He’s running so fast!

—Hard to his legs were once broken.

A. know

B. imagine

C. realize

D. find

答案：

A. know

(答案→)B. imagine

C. realize

D. find

解析：句意:--看！他跑地多快！--很难想像他的腿曾经断过。Know知道； imagine 想像； realize认识到； find找到。根据句意故选B。