They were passed down orally within cultures from generation to generation, so they changed a lot over time.

它们是在某一文化领域内代代口头相传下来的，所以随着时间的推移，它们也发生了很大的变化。

youdao

I spend so much time travelling that I've got packing down to a fine art.

我常常旅行，这就把打点行李学到家了。

《牛津词典》

At about age 15 or so, the men voluntarily began cutting down their nightly sleep time because of pressures from school, work, and other activities.

在大约15岁左右的时候，由于学校、工作和其他活动的压力，这些男性自愿开始减少夜间睡眠时间。

youdao

"A little disappointed last night with the weather that got us, but we fought the weather last night, and it was just not the right time to launch yesterday, so we stood down, got into it today and it really rewarded everybody extremely well."

VOA: standard.2010.02.08

A gig is 10 to the 9, so it does two operations in the length of time it takes light to get from one foot off the table down to the table. That's amazing.

因此光行进一英尺的,时间内电脑可以,进行两次基本运算,这太神奇了。

麻省理工公开课 - 计算机科学及编程导论课程节选

So, I grew up in the South and spent most of my time down in North Carolina.

我在南边儿长大的，但是我大多数时间是在北卡罗莱纳州度过的。

选康内尔大学的理由 - SpeakingMax英语口语达人

So bogged down, no time for people?

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They know most people by that time are so beaten down they give up and stop fighting.

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