— Did you see the boys yesterday afternoon? — Yes. I saw them the fence when I passed.A.

问题补充：

— Did you see the boys yesterday afternoon?

— Yes. I saw them the fence when I passed.

A. climb

B. climbed

C. to climb

D. climbing

答案：

A. climb

B. climbed

C. to climb

(答案→)D. climbing

解析：考查分词用法。See sb doing sth看见某人正在做某事；根据when I passed可知是在过去的一个时间点上发生的事情，那么应该是指正在进行的事情。句意：当我经过的时候，我看到他们正在爬篱笆。