It's caused by volatile organic compounds, or VOCs.

室内空气污染的源头是挥发性有机化合物（简称为VOCs）。

So Aristotle said, " Knowing yourself is the beginning of all wisdom" .

亚里士多德曾说过，" 了解自己是一切智慧的源头。"

It is power seeking to manifest which causes desire.

通过实际行动证实渴望的源头就是命的本能。

Even more alarmingly, its flow is diminishing at source.

更令人担忧的是它的源头水流正在逐渐减小。

What we should be doing instead is preventing conflict in the first place.

而我们应该做的，其实是从源头上阻止冲突的发。

This is where all of the lava is coming from.

这就是所有熔岩的源头。

It was my sister who first had the idea to cycle along the entire Mekong River from where it begins to where it ends.

首先想到要沿湄公河从源头到终点骑车旅行的是我的姐姐。

Located high in the Adirondack Mountains, this lake is the source of the Hudson River.

这个湖位于哈德逊阿第伦达克山脉的高处，是哈德逊河的源头。

One major advantage of using the tide, rather than waves, as a source of energy is that it's predictable: we know the exact times of high and low tides for years to come.

利用潮汐能而不是波浪能的一个主要优势是，它的能源的源头可预测性较好：我们知道接下来很多年的高潮和低潮的时间。

America's drug habit is where the money, the route (ph), all begins.

美国的毒品习惯是金钱和路线的源头。

Experts say there`s a large population of birds in Massachusetts that have no immunity to the virus so that could be a starting point.

专家说，马萨诸塞州有大量鸟类对这种病毒没有免疫力，因此这可能是一个源头。

This has been public land for hundreds of years, and what you'll find interesting is that the River Ouse, which flows into the sea eighty kilometres away, has its source in the common.

这里在几百年前就是公共用地，你会发现有趣的是乌斯河流向80公里外的大海，在common也有源头。

It's located just at the point just where the River Kennet springs out, and we think that the mound was built at the head of the river because this was a really important and perhaps sacred place.

它就位于肯尼特河的源头 ，所以我们认为土丘就建在河头，因为那一个非常重要、亦或许是神圣的地方。

The big difference and any other system that's available out there, the information that you see portrayed on the screen comes directly from the source.

最大的区别和任何其他可用的系统，你看到的被描绘在屏幕上的信息直接来自源头。

But there's a second contingency, a second source of moral arbitrariness that goes beyond the question of whether it's to my credit that I have the talents that enable me to get ahead.

但是还有第二种偶然性，道德偶然因素的第二个源头，它超越了我们今天所讨论的我拥有让我领先于他人的天赋是否是我的功劳。

Dimen Village sits at the origin of Qingshui River.

地处清水江源头的地扪村。

They believe the source of the tsunami must have lain inside the bay itself.

他们认为海啸的源头一定是在海湾内部。

This shows the difficulty of hunting down the virus in a crowded and worried population.

这表明，在熙熙攘攘又充满焦虑的人群中确定埃博拉病毒的源头是有巨大难度的。

And the source of its fertility, the Loess Plateau, is also under threat.

其肥沃源头黄土高原也面临着威胁。

I can't find the source of the bleeding.

我找不到出血的源头。