the doctor said that was a very rare __case___ of the illness（case）they have little money,so they can not __afford___ （支付得起）I _treat___ Daniel as my best friends（treat）the doctor will be __t...最后一个为什么是trained不是training用trained 是被动语态，医生接受训练的意思，而如果用training，就是现在进行时，医生正在训练，后面没有宾语，而且与before 引导的状语从句意思冲突。