We cannot say for sure what will happen.

我们说不准将会发生些什么。

《柯林斯英汉双解大词典》

I think he'll be back on Monday, but I can't say for sure.

我想他星期一会回来，不过我不敢肯定。

《牛津词典》

"I can say for sure that no one else loves me more than you do in this world," stated Sophia tearfully.

“我可以肯定地说，在这个世界上，没有人比你更爱我了。”索菲娅含泪说道。

youdao

"When you can't say for sure whether all the women in the advance provision group actually used the medication, then you're kind of looking at population level effect of a strategy, not the individual effect of a medication."

VOA: standard.2010.03.22

What could you say for sure about it?

哪一点你们比较确定

耶鲁公开课 - 聆听音乐课程节选

Sure. I would say the most important thing is to... for me, to find consistency.

当然，让我说最重要的是……对我来说，是保持连贯性。

健康生活 - SpeakingMax英语口语达人

"The only thing you can say for sure is that you're eating something, " said one taster.

WSJ: Choking Down Chocolate

But we can say for sure that the chancellor has a good friend in Christine Lagarde.

BBC: IMF: 'Great policies - shame about the economy'

Regulators are hard pressed to say for sure what has come over the border.

FORBES: Magazine Article