为什么这个句子情态动词后面可以用不定式?The doctor did what he could to save the

为什么这个句子情态动词后面可以用不定式?The doctor did what he could to save the the doctor did what he could to save it.为什么不是what he could d The doctor did what he could ( ) the dying man.此句中情态动词could后 The doctor did what he could （to save）the child. The doctor did what he could to save the girl who was hurt b 1The doctor did what he could ___(save)the boy,but in vain.t The doctor did all that he could to save the wounded boy.这句话 The doctor did all he could to save the wounded boy.这句话语法上有错 The doctor did what he could_the dying man.A.save B.to save the doctor did what he could ____the dying man 为什么里面要加to sav the doctor did what he could___ the dying man A save B to sa The doctor did what he could___the dying man.A:save B:to sav