How should I know where you've left your bag?

我怎么知道你把包丢在哪儿了？

《牛津词典》

"No," answered he, "how should I know?"

“不。”他回答，“我怎么会知道？”

youdao

She didn't know. How should I know?

她都不知道，我怎么会知道？

youdao

I think you should take the lab sometime, but I don't know how many semesters that you have to take.

我觉得你们应该是不是地去做几次实验,我不太清楚你们要上多少个学期的课

耶鲁公开课 - 基础物理课程节选

We have to know what to pay attention to People who are not good in focusing their attention on the right things -I'm not just talking about attention deficit disorder, I'm talking about some more high-level question of how you know what you should be paying attention to.

我们需要知道哪些值得注意,那些主次不分的人,我谈论的不仅是注意力不足过动症,还有在面对复杂问题时,你如何知道哪些事情值得关注

耶鲁公开课 - 金融市场课程节选

Readers of my blog posts should know why I am deeply skeptical of how the decision to centralize even more decisionmaking authority in Washington D.

FORBES: 5 Myths in Steven Brill's "Bitter Pill" -- Part 2

How rude of me, I should further explain so as not to confuse those who think they know who a person is based on if they voted republican or not.

FORBES: Mitt Romney's Campaign Cancels Staffers' Credit Cards In The Middle Of The Night

No one can say for certain how this change will end, but I do know that change is not something that we should fear.

WHITEHOUSE: President Obama Speaks to the People of Brazil