我已经尽我所能帮助他了。

I've done ___everything ___in my ___power ___to help him.

她不会允许新的德温特夫人成为曼德利的女主人，并且会尽一切努力阻止她。

She will not allow the new Mrs. de Winter to become the lady of Manderly and [will] ___do ___everything ___in her ___power ___to stop her.

政府必须尽其所能保护环境。

The government must ___do ___everything ___in its ___power ___to protect the environment.