It is impossible to know for sure, because official statistics are so inadequate.

不可能确切知道，因为官方统计数据太不充分了。

I think he's Canadian but I don't know for sure.

我想他是加拿大人，但我不确定。

I do not know for sure.

我不确切知道。

But Idon\'t know for sure.

但我也不敢肯定。

Well, we don't quite know for sure.

这个嘛，我们还不太确定。

You don't know for sure Diablo is going back.

你们肯定不知道暗黑破坏神要回来了。

Consider how long it took you to know for sure.

想想确定这个想法你花了多久时间。

The difference in dress - yes, this we know for sure.

衣服可以不同——是的，我们对此确信无疑。

What I know for sure is that what you give comes back to you.

我非常确信一点，就是你付出过什么，你就会有什么回报。

Scientists don't know for sure why we have that crossing over.

科学家不知道为什么我们会如此关联。