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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其他悬而未决的问题是，鼻子是否是全身中唯一受气味影响的部位，而且考虑到气味的非物质性成分，怎样才能够客观地测定它。

Other unanswered questions are whether the nose is the only part of the body affected by odours, and how smells can be measured objectively given the nonphysical components.

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And this looks a lot like the average valence electron energy where the lowest values of electronegativity are in the metallic zone and the highest values of electronegativity are on the nonmetallic zone.

这看起来像是平均电子能,最低的电负性在,金属区最高的电负性在,非电子区。

麻省理工公开课 - 固态化学导论课程节选

And so, Descartes' attempt to establish the distinctness of the mind, the immateriality of the mind, on the basis of this Cartesian thought experiment, I think that's unsuccessful.

所以,笛卡尔试图,用他的卡式思想实验来证明,心灵的独立存在性,和非物质性,我认为这种尝试是失败的

耶鲁公开课 - 死亡课程节选

And to measure the intensity of unequal sharing, we take the difference in electronegativity, which I am going to use the Greek symbol chi for.

要度量非平均的程度，我们考虑电负性的差异，我要用希腊语第22个字母chi来表示电负性。

麻省理工公开课 - 固态化学导论课程节选