I've known him for years, but I still don't know what pushes his buttons.

我已认识他多年，可还是摸不透他的脾气。

《牛津词典》

We don't know what life holds in store for us.

我们不知道等待我们的将是什么样的生活。

《牛津词典》

I just don't know what to do for the best.

我就是弄不清做什么才好。

《牛津词典》

When you're teenagers, you don't quite know what to write on there. Little Os and Xs for kisses and things like that.

VOA: special.2010.02.08

If you don't give me seven hours a week, I don't know what I can do for you.

如果你们一周不学习7个小时，我不知道我能为你们做什么了。

麻省理工公开课 - 固态化学导论课程节选

So why don't you talk about the experience that you had in Israel and also a little bit about what it means to be an Orthodox Jew for those people who don't know maybe the difference between reform and conservative Orthodox.

那何不讲讲你,在以色列的经历,再讲讲,什么是犹太教正统派,向那些可能不知道,改革以及保守正统派的区别的人解释一下。

普林斯顿公开课 - 人性课程节选

So it's important to get everybody participating, and a certain number of people in that 42 percent we were talking about don't even know if this is necessary, don't know that it applies to them, don't know what it entails for them, don't know what the advantages are for themselves.

NPR: Nearly Half The Country Doesn't Know Health Law Exists

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

CNN: Five things we learned from the Benghazi hearings

It's just too short, barely reaching from the back of the PowerBook to the left side of the keyboard (this reviewer is left-handed, and especially militant about products that don't offer easy access for southpaws.) I don't know what it would have cost Apple to add another foot of cable, but it would have been worth it.

CNN: Review: Apple Pro Mouse