youdao

地球历史上的这次重大灾难以物种的大量消亡为标志；当时，地球上多达一半的物种都灭绝了。

This break in Earth's history is marked by a mass extinction, when as many as half the species on the planet became extinct.

youdao

而是一种以甲烷和乙烷为标志的烃类物质的大气循环。

It is instead an exotic climate of hydrocarbons that features methane and ethane.

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We're talking about a culture when we're talking about the Greeks, which is most strikingly signified by the language that is spoken.

当我们谈论希腊人时我们是谈论希腊文化,是严格以所使用的语言为主要标志的

耶鲁公开课 - 古希腊历史简介课程节选

If you would like to flag them as private, because you just don't want your classmates to see what you're asking, you can certainly do that.

如果你想要把它们标志为私有的，不想让你的同学们,看到你问的问题，你当然也可以这样做。

哈佛公开课 - 计算机科学课程节选