We don't know for sure how much mass our Sun's lost over the last four billion years.

我们不知道我们的太阳在过去的40亿年里损失了多少质量。

youdao

We'd probably know for sure whether someone was shooting at the president from that famous grassy knoll.

我们可能确定是否有人正在从那个著名的草地山丘草地上向总统射击。

youdao

Do you remember all years when scientists argued that smoking would kill us but the doubters insisted that we didn't know for sure?

还记得那些年吗？当初，科学家提出吸烟会导致死亡，而怀疑者们却坚持认为我们还不能确认这一点。

youdao

Experts do not know for sure about his mother,Caterina.

VOA: special.2010.09.15

It's been disputed and one doesn't know for sure.

尽管这点还存在争议。

耶鲁公开课 - 文学理论导论课程节选

it's Shopbot for people, you know, make sure things sell,

对人们来说，那就是个比价器，确保东西卖得出去，

在布鲁明戴尔百货 - SpeakingMax英语口语达人

We do know for sure by now that was the right way to create jobs.

FORBES: How to Create Jobs: Stop Misguiding the Animal Spirits of Entrepreneurs!

Hard to know for sure, given that the SBA keeps track of the figures.

FORBES

We know for sure that there are differences between the male and female brain.

BBC: Art appreciation 'a gender issue'