all we can to
问题描述：
all we can to
很常见的说法是：
We should do all we can to help those who are in trouble.
为什么不是：
all we can do to help..
all that we can to help..
all that we can do to help..
what we can to help..
what we can do to help..
答
首先,all that we can do to help..＝what we can do to help..
其次,这里定语从句的关系词that是作宾语的,可以省略,而动词do因为跟前面一样也可以省略,于是变成all we can to help