我不确定他在说哪首歌。

I'm not sure which song he's talking about.

youdao

我不确定他是否够格做我们的代表。

I'm not sure if he is qualified enough to be our representative.

youdao

我不确定他是否还活着。

I'm not sure that he is still alive.

youdao

If he had all of that,it's not so clear to me that it would be the wrong thing to say that, by golly,this is Napoleon.

如果他都拥有这些，那我就不太确定，这么说是否错误了，天哪，这是拿破仑。

耶鲁公开课 - 死亡课程节选

I mean, there's John Nash who's the, well, I don't... I think he won a Nobel Prize.

有一个校友叫约翰·纳什，我也不确定他得没得诺贝尔奖。

知道约翰·纳什吗？ - SpeakingMax英语口语达人

I'm not sure if he still lives in San Francisco.

我不确定他是不是依然住在旧金山。

罗宾·威廉姆斯的家 - SpeakingMax英语口语达人