The doctor did everything they could the dying boy’s life but they failed.Asaving B．to s

问题补充：

The doctor did everything they could the dying boy’s life, but they failed.

A．saving B．to save C．saved

答案：

解析：句意:医生做所有他们能做的事来救这个即将死去的孩子的生命，但是他们失败了。在这句话中they could 是一个定语从句，修饰先行词everything。从句中省略了动词do；动词不定式在这里做目的状语，表示为了…。故选B。