我本应该知道不该信任他的。

I should have ___known ___better than to trust him.

成年人应该知道不该在公共场合争吵。

Adults should ___know ___better than to argue in public.

你年纪大了，应该知道不该犯这样的错误。

You're old enough to ___know ___better than to make such mistakes.