同学你好，该知识点来自沪江网校《英语零基础直达大学六级【3年随心畅学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
The three college students    did   what they could    to rescue the two children    although they were in danger.

The three college students 主语
did谓语，表示“做”
what they could宾语从句，”他们能做的“
to rescue the two children 不定式作目的状语
although they were in danger    although引导让步状语从句

宾语从句的谓语是could do，只不过这里do因为避免和前面的did重复而省略了
比如
He is saving every cent that he can (save) to buy a house.

祝同学学习进步~