I should have known the answer to his simple question.

我本应该知道他那个简单问题的答案的。

youdao

Maybe he should have known it.

也许他本应该知道这件事。

youdao

I mean to say, you should have known how he would react!

我的意思是说，你本应料到他会作何反应！

《牛津词典》

I shouldn't havebrought you here. I should have known it was goingto be some bullshit hassle!

VOA: standard.other

Some of the things I said--you'd probably say, well I should have known that an insurance company would have to do that, but it isn't.

对于我说的一些东西，你可能会说，我早就知道,保险公司会如此操作，但事实并非如此。

耶鲁公开课 - 金融市场课程节选

You should have known better.

你早该知道的。

I should have 实战 - SpeakingMax英语口语达人

But we should have known that already through our past experience with the political process.

FORBES: The Looming Failure of Obamacare, Part 3: Rent-Seeking

How we should have known was explained in high resolution a few months back.

FORBES: The Small Government Establishment Joins the Establishment

To be fair to Draghi, people getting excited about this meeting should have known better.

FORBES: ECB : We'll Do What It Takes. Kinda. Sorta. Later.