A UN official said he thought it was an open question whether sanctions would do any good.

一位联合国官员表示，他认为对于制裁是否能够起到作用这个问题，尚无定论。

I don't believe that markets are efficient, and it doesn't really seem like it should be an open question.

我不相信市场是有效的，这似乎也不是一个开放式的问题。

That's still an open question.

这仍然是个未解决的问题。

It's an open question.

这是个难以回答问题。

How they got going so fast is an open question.

他们是怎样达到这么快的速度仍是一个待解决的问题。