Floyd said he could not breathe many times based on videos recorded by people watching the incident.

根据目击该事件的人录制的视频来看，弗洛伊德好几次都说自己无法呼吸。

This clean and simple mathematical definition has just one problem, Earth is a terrible thing to base time on.

这个清晰而简单的数学定义只有一个问题，地球非常不适合用来作为计时的基础。

It's a rectangle! And the area of a rectangle is just its base times its height.

是一个长方形！和矩形的面积 底等于高。

An area of a line, if you were to just draw a line, you'd say well, area is height times base.

一条线的面积， 如果你只是画一条线，你会说，面积是高度乘以底。

And by that I mean I always base my arrival to the airport on the boarding time of my flight not the departure time.

所以，我一般都是根据航班登机时间到达机场，而非起飞时间。

It's important to note that government policies and plans can evolve over time based on changing demographics, health needs, and emerging health challenges.

值得注意的是，政府政策和计划可能会随着人口结构、健康需求和新出现的健康挑战的变化而不断变化。

Their mention of astronomy concerns the telling of time based on the stars in the sky as well as the link between stars and celestial movements and the season.

他们提到的天文学涉及到根据天空中的星星来判断时间，以及星星与天体运动和季节之间的联系。