Today's circuses usually have three rings.

VOA: special.2009.01.11

It wouldn't be the same if I turned it upside down because the carbons - the rings here, the pentose's would all be turned over, the chemistry would look different and the sequence of bases would look different.

记住单链倒过来,就和原来不一样了,这是因为碳原子和糖环结构,戊糖会翻转,使得这个化学结构看起来不一样了,碱基的顺序也不一样了

耶鲁公开课 - 生物医学工程探索课程节选

there's rings you could swing on.

你可以在上面摇荡，

圣莫妮卡的海滩 - SpeakingMax英语口语达人