但有个问题，金星凌日很难得。

But there was a problem. Transits of Venus are rare.

youdao

但有个问题：怎样才算是个完美的、持续的、高效的、环境优美的和最理想的城市呢？

The question is: what are the characteristics of an ideal, sustainable, efficient, environmentally-friendly, optimal city?

youdao

但有一个问题：和水星凌日不同的是，金星凌日是罕见的，大约每隔一百年会成对出现八年的时间。

But there was a problem: transits of Venus, unlike those of Mercury, are rare, occurring in pairs roughly eight years apart every hundred or so years.

youdao

Nobody knows, but there's a theory which won't answer your question but will put it into a broader context.

没有人知道答案,但有这么个理论,它无法回答你的问题,但却能让你从更宽广的视角来看这个问题

耶鲁公开课 - 心理学导论课程节选

But that raises a third philosophical question: What is the moral work that consent does?

但这样又引发了第三个哲学问题：,征得同意有何道德作用？

耶鲁公开课 - 公正课程节选

23456789 All right, here I gave it a big number, 123456789. And again, I don't want to bore you, but you can see what's going on here with this trend.

我给出一个大数字，又一次，我并不想令你们感到枯燥，但你们可以自己看看会发生些什么,这儿有个有趣的问题。

麻省理工公开课 - 计算机科学及编程导论课程节选