The doctor did save the patient’s life.
A. that he could do
B. all what he could
C. all he could to
D. which he could
网友回答
A. that he could do
B. all what he could
(答案→)C. all he could to
D. which he could
解析：考查省略句和不定式做目的状语：句意：医生尽了最大努力救病人的生命。All是这句话的宾语，he could是定语从句修饰all，定语从句省略了关系代词和动词do，不定式这里是目的状语，选C。