These are elements that have yet to be isolated These are elements that are unstable.

这些元素还没有被提取出来,这些元素很不稳定。

麻省理工公开课 - 固态化学导论课程节选

I really don't know at this point but uh, I don't know.

目前我还不清楚，还没有想好。

哥伦比亚大学的教程 - SpeakingMax英语口语达人

Now there was a time when people thought fat was bad and it didn't-- and people didn't really understand there were different kinds of fat, or they didn't realize that different kinds of fat had different impacts on health.

曾经有段时期,人们认为脂肪是有害的,它不能...,人们当时不知道脂肪还分不同种类,所以就没有意识到,不同的脂肪对人体有不同的影响

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

No, I haven't.

不，我还没有。

Have you 实战 - SpeakingMax英语口语达人