在这重要的一亿年的周期内缺乏化石（记录），关于这一点，有一种解释是早期的动物是软体动物，所以它们无法形成化石。

One interpretation regarding the absence of fossils during this important 100-million-year period is that early animals were soft bodied and simply did not fossilize.

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新南威尔士大学的一项新研究发现，在工作周期间，澳大利亚的父亲们每天单独陪伴孩子的时间平均只有一分钟多一点。

A new study from the University of New South Wales has discovered that during the working week, Australian fathers only spend an average of just over a minute each day alone with their children.

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上午九点半的时候，完整的红黄绿信号灯变换周期大概为140秒。

At 9:30 am, the full red/yellow/green signal cycle might be 140 seconds.

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Cells can stop in their lifetime at some point in the cell cycle and persist for long periods of time.

细胞生命期可以停止在细胞周期的某个点,并保持很长时间

耶鲁公开课 - 生物医学工程探索课程节选

Second thing, we started talking about the periodic table and I believe that it's a hallmark of any educated person in the 21st century who is technically literate to know the periodic table by heart.

第二点，我们之前讨论过元素周期表,我相信这是个标志性的特征,对于那些在21世纪里,用心去学习,元素周期表的人来说。

麻省理工公开课 - 固态化学导论课程节选