I don't know for certain why Carl Dadisman, the owner, wouldn't stop Daddy from sitting down.

我不知道出于什么原因，卡尔·达迪斯曼——这家店的店主——并不阻止爸爸坐下。

youdao

I don't know for certain if she's coming.

我并不确切知道她是否会来。

youdao

So, honestly, I don't know for certain yet.

所以，实话说，我都不知道究竟会是谁。

youdao

We don't know for certain. But what might have happened to lead to the two different editions?

我们不能确切知道，但可能发生过什么,导致了这两个不同版本？

麻省理工公开课 - 媒体、教育、市场课程节选

We don't know for certain whether the company just mismanaged its crisis handling or forged ahead knowing that problems were coming.

ENGADGET: Ginsu knives, psychic hotlines and a $90 tablet: the story behind the Matrix One (update: more details)

"It might contain traces of horsemeat, but we don't know for certain at the moment if this is the case, " said Esther Filon, a spokeswoman for the Dutch food authority.

BBC: Horsemeat scandal: Dutch uncover large-scale meat fraud

Since no one at either institution is willing to discuss this and I don't blame them, because I would be embarrassed too I don't know this for certain.

WSJ: Elizabeth Wurtzel: Tough Times for Big Law