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Half of the students in four large philosophy classes read an article on the ethics of factory-farmed meat, optionally watched an 11-minute video on the topic and joined a 50-minute discussion.

在四节大型哲学课上，一半学生阅读了一篇关于工厂化养殖肉类的伦理文章，非强制性观看了一段11分钟的视频，并开展了50分钟的讨论。

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End date (and optionally time).

结束日期(和可选的时间)。

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And after all that, optionally pour a few beer or sugar-laden coke down your mouth.

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For example, if a customer uses an ATM, a notification can be pushed optionally to the mobile device.

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For the greater freedom of quick charging it is possible to optionally equip the vehicle with a quick-charging function.

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