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Passage 2There is no creature that does not need sleep or complete rest every day.If you want to knowwhy, just try going without sleepfor a long period of time. You will discover thatyour mind and body would become loo tired to work properly. You would become imitable and find it hardto think clearly or concentrate on your work. So sleep is quite simply the time when the cells of your bodyrecover from the work of the day and build up supplies of energy for the next period of activity.One of the things we all know about sleep is that we are unconsciousin sleep. We do not know whatis going on around us. But that doesn't mean the body stops all activity. The important organs continue towork during sleep, but most of the body functions are slowed down.For example, our breathing becomes slower and deeper. The heart beats more slowly, and the bloodpressure is lower. Our arms and legs become limp and muscles are at rest. It would be impossible for ourbody to relax to such an extent if we were awake. So sleep does for us what the most quiet rest can not do.Your body temperature becomes lower when you are asleep, which is the reason people go to sleepunder some kind of covers. And even though you are unconscious, many of your reflexes still work. Forinstance, if someone tickles your foot, you will put it away in your sleep, or even brush a fly from yourforehead. You do these things without knowing it.66. If you don't have as much sleep as your body needs, you will ________ .
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In the clause".. that we are unconscious in sleep"(Paragraph 3), the word "unconscious" means _______ .
Passage 3Space is a dangerous place , not only because of meteors but also because of rays from the sun and other stars. The atmosphere again acts as our protective blanket on earth. Light gets through, and this is essential for plants to make the food which we eat. Heat , too , makes our environment endurable. Various kinds of rays come through the air from outer space，but enormous quantities of radiation from the sun are screened off. As soon as men leave the atmosphere they are exposed to this radiation. But their spacesuits or the walls of their spacecraft, if they are inside, do prevent a lot of radiation damage.Radiation is the greatest known danger to explorers in space. The unit of radiation is called”rem”. Scientists have reason to think that a man can put up with far more radiation than 0.1 rem without being damaged; the figure of 60 rems has been agreed on. The trouble is that it is extremely difficult to be sure about radiation damage- a person may feel perfectly well, but the cells of his or her sex organs may be damaged, and this will not be discovered until the birth of deformed children or even grandchildren. Missions of the Apollo flights have had to cross belts of high radiation and ，during the outward and return journeys, the Apollo crew accumulated a large amount of rems. So far , no dangerous amounts of radiation have been reported, but the Apollo missions have been quite short. We simply do not know yet how men are going to get on when they spend weeks and months outside the protection of the atmosphere, working in a space laboratory. Drugs might help to decrease the damage done by radiation, but no really effective ones have been found so far.71. According to the first paragraph, the atmosphere is essential to man in that ______ .
Passage 4How men first learned to invent words is unknown; in other words, the origin of language is amystery. All we really know is that men, unlike animals, somehow invented certain sounds to expressthoughts and feelings, actions and things, so that they could communicate with each other; and that laterthey agreed upon certain signs, called letters, which could be combined to represent those sounds andwhich could be written down. Those sounds, whether spoken, or written in letters, we callwords.The power of words then , lies in their associations---the things they bring up before our minds.Words become filled with meaning for us by experience; and the longer we live, the more certain words recall to us the glad and sad events of our past; and the more we read and learn, the more the number of words that mean something to us increases.Great writers are those who not only have great thoughts but also express these thoughts in words which appeal powerfully to our minds and emotions. This charming and telling use of words is what we call literary style. Above all, the real poet is a master of words. He can convey his meaning in words which sing like music, and which by their position and association can move men to tears." We should therefore learn to choose our words carefully and use them accurately, or they will make our speech silly and rude.76. The origin of language ________ .
What is true about words?
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