有一位全程导游，可安排非强制性的进餐和观光。

There is a tour guide throughout the trip who will organize optional dinners and sightseeing.

《柯林斯英汉双解大词典》

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。

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.

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这是一个三年级课程，非强制性。

Local Politics . This is a senior-year course.

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She baptizes the entire domain of non-auditory sensual experience that the Lady so forcefully avoids.

她给这位女士所有非听觉的地方都进行了洗礼,而那都是女士强制自己去避免的。

耶鲁公开课 - 弥尔顿课程节选

And it's almost always used with those unenforceable kinds of things.

这种形式常常用于非强制性的指示。

耶鲁公开课 - 旧约导论课程节选