如果你不知道自己的胆固醇水平，最好去查一下。

If you don't know your cholesterol level, it's a good idea to have it checked.

《柯林斯英汉双解大词典》

如果你不知道什么是鹰头狮，请看图片。

If you don't know what a Gryphon is, look at the picture.

youdao

准备出国旅行真的会很有压力，尤其是如果你不知道会发生什么。

Preparing to go traveling abroad can be really stressful, especially if you don't know what to expect.

youdao

It's very exciting, but if you think you know everything you don't need to learn, you don't belong to us. I always need to learn.

这很令人兴奋，但如果你认为,你什么知道，你不需要学习了，那么请你退出百度，因为人总是在学习。

斯坦福公开课 - 百度CEO李彦宏演讲：全球最大搜索引擎的发展课程节选

If you don't know why you're about to eat cake like that you will soon, but you know this.

如果你现在还不知道为什么将要吃到那样的蛋糕,很快就会知道的，你清楚这一点。

哈佛公开课 - 计算机科学课程节选

Mr. Carl Icahn: Well, it's hard to recommend how to invest at this time without knowing how much capital you have.

伊坎先生：嗯，在当今形势下,如果不知道你有多少资本,那就很难给你投资建议。

耶鲁公开课 - 金融市场课程节选