They do what they can to help others.为什么不是They do what they can do to help others?
问题描述：
They do what they can to help others.为什么不是They do what they can do to help others?
what they can 是什么成分?为什么不要加第二个do?
答
第一个do和第二个do意义相同,但是第一个do不可省略,第二个do经常省略,是为了避免用词重复.写出来do不如省略掉更自然.