You know how many times has AT&T tried to introduce picture phones just to have people go, “No, I don't want them to see me !”

你们可知道美国电信公司试验了多少次才实现了可视通话，结果人们却都说：“不，我不想别人看到我！”

youdao

If you are traveling a lot and don't always know the language of the country you are visiting, then this T-shirt is for you.

如果你是一个酷爱旅行者，但并不是每个你到的国家的语言你都懂得，那么这款问路帮手T恤非常适合你。

youdao

Don 't wait... Because you don't know how long it will take.

不要等待，因为，你不知道等待需要花费多少的时间。

youdao

"Don't pretend that you don't know what you have done to me."

VOA: special.2009.05.30

You might know already that you've got a 50 percent chance of having it, but you don't know whether you yourself have it.

你可能已经知道了,自己有50%的机会获得这种基因，但你不知道你有没有。

耶鲁公开课 - 死亡课程节选

Or perhaps, you could be trying to explain that you don't know whether you can do something or not by a certain date.

又或者，你正在试图解释你没法确定你是否能在一个指定日期前做完某件事。

I don't know 课堂 - SpeakingMax英语口语达人

You just don't know in the Derby because you don't know who's going to get into racing trouble.

NPR: Louisville Coach Chasing Derby Win As A Co-Owner

Don't say what you don't know for sure until it's finally decided.

CNN: Five things we learned from the Benghazi hearings

One of the main problems with looting is that if a site is undiscovered, you simply don't know what you don't know.

CNN: Opinion: Illegal antiquities trade funds terrorism