我不确定英文短语

I am not yet sure/certain.We're not yet sure exactly who the rescued hostage is.目前我们还不清楚获救人质的身份。

I'm not sure whether I should tell you this.

我拿不准该不该把这事告诉你。

I'm not sure that this is the most valuable use of my time.

我不能肯定我的时间这样来安排最有价值。

I think this is their house, but I'm not sure.

我想这是他们家，但不敢肯定。

One should never criticize if one is not sure of one's facts.

一个人如果对自己掌握的事实没有把握，就绝不该随便批评。

Ask me if you're not sure how to do it.

你要是拿不准怎么干，就问我。

请LZ采纳楼下的“I'm not sure",I'not sure缺少谓语，语法错误。