我不确定的英文短语

I'm not sure she believes me. She probably just thinks I've gone off the deep end.

我不确定她是不是相信我。她可能只是觉得我神志不清了。

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。