状语从句的本质就是用一个句子代替了原来一个词或者短语所做的状语。而状语的本质就是用来描述谓语动词状态的语言。比如“昨天吃饭”中的“昨天”就是描述“吃饭”者动作的时间状态；“在家吃饭”就是描述“吃饭”这个动作的“地点”状态；“如果天黑就吃饭”是在描述“吃饭”这个谓语动作的“条件”状态。所以所谓状语，就是描述谓语动词状态的语言，所谓状语从句就是描述谓语动词状态的一个句子。而谓语动作的状态总体可以分为九种：时间，地点，原因，结果，条件，目的，方式，让步，比较。 这些就是我们说的状语，而如果我们需要用一个句子来表示这个状语，这时候就需要一个状语从句。因为一个句子中只能有一个谓语动词，而状语本身就是修饰谓语动词的，所以它本身不可能含有谓语动词，但是它却可以含有一个动作，这时这个动作就只能作从句里的谓语动词了。比如“如果天黑，我们就吃饭”，天黑在中文中就是一个动词，吃饭又是一个动词，而英文一个句中只能出现一个谓语动词，怎么办呢，于是语言学家就希望将别的动词区分出来告诉读者这个词不做谓语动词，怎么告诉呢，就在这个词的前边加了一个“if”，于是就变成了“If it’s dark, we’ll have dinner.”当读者看到“if”之后，就知道if后面有一个动词做if从句的谓语动词，而另外一个词做整句话的谓语动词。这就是所谓条件状语从句的由来，而其他的从句其实也都是找了一个词来指示读者后面有一个动词它不做谓语动词，而是做从句的谓语动词。这就是所谓从句的由来和表现方法。
It was another 11 years before scientists finally adapted the French patent for the US.
As the clouds roll in, a leisurely round of golf can become a terrifying dice with death-out in the open, a lone golfer may be a lightning bolt’s most inviting target.
But while rockets are fine for research, they cannot provide the protection from lightning strikes that everyone is looking for.
Where seasonal agriculture was practised , the solar year became more crucial.
Given that the international conference at London Zoo was held 30 years ago, this is pretty slow progress, and a long way off Tudge’s target of 2,000.
And since he needed a summer project for his student Emilio Graff, investigating the possibility of using kites as heavy lifters seemed like a good idea.
Flax ropes and cords had such great strength that they were used to bind together sections of hollowed-out logs to create huge ocean-going canoes, and to provide rigging, sails and lengthy anchor warps for them. (Test Plus2- Reading- Multiple-choice, Choose Multiple Answers 1)
The motion of a pendulum rocks this device so that it catches and then releases each tooth of the escape wheel, in turn allowing it to turn a precise amount.
The way rewards are distributed should be transparent so that employees perceive that rewards or outcomes are equitable and equal to the inputs given.（剑6text7）
Such associations can be powerful enough so that odours that we would generally label unpleasant become agreeable, and those that we would generally consider fragrant become disagreeable for particular individuals.
Between 1940 and 1959, overfishing led to crashes in salmon populations so severe that in 1953 Alaska was declared a federal disaster area.
The biologists Lewis Thomas, wrote, ‘Ants are so much like human beings as to be an embarrassment.’
No one minds mistakes or ignorance as long as you are prepared to learn from them.
At least as long as a biological system has the ability to renew itself it could actually become older without ageing; an organism is an open, dynamic system through which new material continuously flows.
Company leaders have to be careful that they do not have one set of practices for those in the office and another for those who telecommute. (Test Plus2- Listening- Highlight Correct Summary 1)
Old people should be encouraged to live in a nursing house so that they can enjoy professional care and first-rate facilities.
Although the same law holds for a living organism, the result of this law is not inexorable in the same way.
Although more and more people attain an advanced age as a result of developments in medical care and better nutrition, the characteristic upper limit for most remains 80 years.
In spite of its importance to our emotional and sensory lives, smell is probably the most undervalued sense in many cultures.
This is true even if the individual never actually exercises his or her option to turn the noise off. Just the knowledge that one has control is sufficient.
However experienced you or your staff may be in a particular field, if you are thinking of introducing a service to a new area, it is important to find out what the local population thinks about it first. (Test Plus1- Read Aloud 1)
Although tea was originally grown only in certain parts of Asia- in countries such as China, Burma and India- it is now a key export product in more than 50 countries around the globe. (Test Plus1- Summarize Written Text 1)
Whereas they have been long-thought to live in old-growth forests, they are now building up quite an urban population. (Test Plus2-Listening: Fill in the Blanks 1)
Paleontologists still argue about the origins of major groups, though new fossil finds since Darwin’s time have cleared up many of the disparities in the fossil record. (Testbulider 1- Reading- Re-order Paragraphs 2)
Just as we protect less able human beings, so we should safeguard the welfare of other weaker species.
In developed countries, much larger quantities of fish are consumed than as the case a century ago when fish only featured on the menu once a week. (than… 倒装) (Test Plus1- Summarize Written Text 2)
And the older and larger the settlement, the more dark earth there is. (Test Plus1- Reading- Multiple-choice, Choose Multiple Answers 2)
Animals which save energy by hibernation or lethargy live much longer than those which are always active.
His designs won more acclaim than those of his fellow colleagues.
Moreover, recent evidence suggests that the crop farming of ants may be more sophisticated and adaptable than was thought.
The more effort put in and the wider the whole school involvement, the more substantial the results are likely to be.
European countries are becoming increasingly concerned by major threats to European forests, threats which know no frontiers other than those of geography or climate: air pollution, soil deterioration, the increasing number of forest fires and sometimes even the mismanagement of our woodland and forest heritage.
The wind was blowing at a gentle 16 to 20 kilo metres an hour, little more than half what they thought would be needed.
The noise was quite disruptive at first, but after about four minutes the subjects were doing just as well on their tasks as control subjects who were not exposed to noise.
We are much more able to ‘tune out’ chronic background noise, even if it is quite loud, than to work under circumstances with unexpected intrusions of noise.
In the Glass and Singer study, in which subjects were exposed to bursts of noise as they worked on a task, some subjects heard loud bursts and others heard soft bursts.