Question

请问这句的句子成分是？越详细越好，谢谢。

They've done everything they can possibly think of
凡是能想到的，他们都去做了

Answer 1

主句:They've done everything 定语从句:they can possibly think of修饰everything，前面省略了连接代词what或that。
如果不省略:
They've done everything (what) they can possibly think of.这里what代表everything，又作of的介词宾语。

Answer 2

They（主）e done（谓） everything（宾） 【they主 can possibly（状） think of（谓）定语从句（省略引导词that)】

Answer 3

定语从句，主语they，谓语have done，宾语everything；从句they can possibly think of作everything的定语，省略了that/which/..（在从句中作宾语）