More than 90 percent of the matter that makes up trees was once water and free-floating atmospheric carbon dioxide.
形成一棵树所需的物质里，90%都来自于水分和空气中的二氧化碳。
He states that most rats, loyal to their social groups and habitats, will try going back home once water subsides.
他指出，由于大多数老鼠都很忠于自己的群体和栖息地，所以水退后，它们也将设法返回老巢。
Tractors are tilling the land and building earthen rows that will serve as levees once water flows into these fields.
拖拉机在耕地，并且建起一道道田埂，等水流进这些农田时，这些田埂就能起到河堤的作用。
It takes just two or three big waves to signal doom: once water flows behind the defences, even the thickest ramparts are swift to collapse.
一两个大浪就可以宣告末日将至：海水一旦流过城墙，再厚的城墙也难逃一塌。
Add oils once water level has been reached. Start with 5-10 drops; adjust depending on the size of the water container and your scent tolerance.
加入精油在理想量的水中，先从5 -10滴中开始，根据水的容量和对香味的容忍度来调整。
Stronger rivets might have slowed the sinking process, but once water began flooding six of the Titanic's compartments, it was only a matter of time before the ship went down.
坚固的铆钉可能会减缓下沉的过程，但是一旦海水浸入泰坦尼克号的6个舱室，沉船只是一个时间问题。
Change it if the attrition is too much, or once water leaks, it may lead to sudden cooling of the furnace lining, which may directly influence the using effects of the furnace lining.
如果磨损过多，必须更换。否则一旦漏水，就会造成炉衬的急冷，直接影响炉衬使用效果。
Once the vegetables start to cook add in a couple of tablespoons of water.
一旦蔬菜开始加热烹调，就加入几汤匙水。
The water is fine once you're in!
你一旦下了水，就会觉得水里挺舒适。
Water the plant once a week if you are to get fruit in the autumn.
如果你想秋天收获果实就要每周给植物浇一次水。
Once known, it spread rapidly, driving out water clocks but not solar dials, which were needed to check the new machines against the timekeeper of last resort.
一旦被人所知，它就迅速传播开来，替代了水钟，但却没有替代日晷，日晷被用来将新机器与原来的计时方法进行对照检查。
We have to water this cactus once a month.
我们必须每月给仙人掌浇一次水。
Try to drink some water at least once every hour.
尽量每小时至少喝一次水。
He picked up two plastic buckets and rushed to the center of the village, where a fire engine arrives once a day to provide water for residents.
他提起两个塑料水桶奔向村子的中心位置，消防车每天都会来这里一次，为居民们提供水源。
I'm hardly a clotheshorse, but the few new items I buy once again trumped the amount of water flowing from my faucets each day.
我不是一个讲究穿衣的人，但我买的几件新衣服又一次超过了每天从水龙头流出的水量。
Where 50-kilogram king salmon once fought their way up waterfalls to lay their eggs in gravel beds, there now are only concrete walls holding back still water and deep beds of muddy deposits.
50公斤重的大马哈鱼王曾经奋力爬上瀑布，把卵产在砾石床上，现在只有混凝土墙挡住静止的水和深深的泥床。
Radars used to track storms can detect water in the atmosphere only once it has condensed into clouds or raindrops.
用于跟踪风暴的雷达只能在大气中凝结成云或雨滴后才能够探测到水。
In a normal water phase, rivers eventually empty into oceans, and once in the oceans, the Phosphorus gets absorbed by water plants like algae.
在正常水相下，河流最终流入海洋，而一旦进入海洋，磷就被藻类等水生植物吸收。
Once, people used too much underground water.
过去，人们使用了太多的地下水。
Rain water was once considered to be good for the complexion.
雨水曾一度被认为对肤色有益。
We water the flowers once a week.
我们每周给花浇水一次。
Photographic evidence suggests that liquid water once existed in great quantity on the surface of Mars.
照片证据表明，液态水曾大量存在于火星表面。
Since most planetary scientists believe that water is essential to life, the presence of jarosite means that one prerequisite for life was once present on Mars.
由于大多数行星科学家认为水是生命的基本要素，因此黄钾铁矾的存在意味着火星上曾经存在出现生命的先决条件之一。
A thirsty crow once came upon a pitcher with very little water in it.
有一次，一只口渴的乌鸦碰巧遇到一只大水罐，里面只有一点点水。
At once like an eel she slid between Starkey's legs into the water.
她像条鳗鱼似的，立刻从斯塔奇两腿之间滑入水中。
Wuxi is famous for its water but it once had trouble because of water.
无锡因水著名，也曾因水而困。
We should drink some water at least once every hour and try to make our water last longer in the Sahara.
我们应该至少每小时喝一次水，并努力使我们的水在撒哈拉沙漠中保存更长时间。
The Toad retraced his weary way on foot, and related his disappointing experiences to the Water Rat once more.
托德拖着疲惫的步伐返回，又向水鼠兰特讲述了他那些令人糟心的经历。
After resting for a glass of water, the boy tried to move it once more.
喝了杯水，休息了一下后，男孩再次尝试挪动它。
After resting for a glass of water, the boy tried to move it once more.
喝了杯水，休息了一下后，男孩再次尝试挪动它。
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