They tried their best to do __________ help us. A. that they could B) all that they couldThey tried their best to do __________ help us. A. that they couldB) all that they could C. what they could to D. what they could请高人解释下为什么是C呢?
问题描述：
They tried their best to do __________ help us. A. that they could B) all that they could
They tried their best to do __________ help us. A. that they could
B) all that they could C. what they could to D. what they could
请高人解释下为什么是C呢?
答