但是进入名牌大学的机会只有一次。

But there is only one chance to get into a famous university.

youdao

创造第一印象的机会只有一次。

You have only one chance to make a first impression.

youdao

留下好的第一印象的机会只有一次。

You only get one chance to make a first impression.

youdao

There we go. Now if I do this, an infinite number of times, we should get roughly 50/50, but now we have the ability to do things only once in awhile.

开始，如果我们，不停地按这个按钮，我们大致会有一半的机会听到猫叫，但是我们每次只有一次按按钮的机会。

哈佛公开课 - 计算机科学课程节选

And then other people are really excited because it's a once-in-a-lifetime opportunity

而另外一些人真的很兴奋，因为这是一个一生只有一次的机会，

正准备奥运会 - SpeakingMax英语口语达人