They did what they could----the poor children.为什么填to help 不填

to help。。。The did (what they could) to help the poor children。。。what they could 是宾语从句。所以。简化整个句子是They did sth to help the poor children。。。翻译起来就是。他们尽其所能地帮助贫穷的孩子。