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Throughout history man has had to accept the fact that all living things must die. And people now live no (1) than they (2) to. It is true that all living things still show the (3) of aging, which will eventually result (4) death. Aging is not a disease, but as a person passes maturity, the cells of the body and the (5) they form do not (6) as well as they did in childhood and adolescence. The body provides less (7) against disease and is more prone (8) accident. A number of related causes may (9) to aging. Some cells of the body have a fairly long life, but they are not (10) when they die. (11) a person ages, the number of brain cells and muscle cells decrease. Other body cells die and are (12) by new cells. In an aging person the (13) cells may not be as able to develop or as capable (14) growth as those of a young person. Another (15) in aging may be changes within the cells themselves. Some of the protein chemicals in cells are known to change with age and become less elastic. This is why the skin of old people wrinkles and (16) loose. This is also the reason old people (17) in height. There may be other more important chemical (18) in the cells. Some complex cell chemical, such as DNA and RNA, store and pass (19) information that the cells need. Aging may affect this (20) and change the information-carrying molecules so that they do not transmit the information as well.
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Are you aware that you actually possess six senses The sixth is a muscular sense (1) for your muscles intelligently to the exact (2) necessary for each action you perform. For example, when you reach (3) an object, the sensory nerves (4) the muscles to the brain and stop your hand at the correct (5) . This automatic perception of the position of your muscles (6) relation to the object is your muscular (7) in action. Muscles are bundles of fibers (8) from one five-thousandth of an inch to about three inches. They have three (9) characteristics: they can become shorter and thicker; they can (10) ; and they can retract to their original positions. (11) a high powered microscope, muscle tissue is seen (12) long, slender cells with a grainy texture like wood. More than half of a person’s body is (13) of muscle fibers, most of (14) are involuntary, in other words, work without (15) direction. The voluntary muscles, those that we move consciously to (16) particular actions, (17) more than five hundred. Women have only 60 to 70 percent as much (18) as men for their (19) mass. That is (20) an average woman can’t lift as much, throw as far, or hit as hard as an average man.
Throughout history man has had to accept the fact that all living things must die. And people now live no (1) than they (2) to. It is true that all living things still show the (3) of aging, which will eventually result (4) death. Aging is not a disease, but as a person passes maturity, the cells of the body and the (5) they form do not (6) as well as they did in childhood and adolescence. The body provides less (7) against disease and is more prone (8) accident. A number of related causes may (9) to aging. Some cells of the body have a fairly long life, but they are not (10) when they die. (11) a person ages, the number of brain cells and muscle cells decrease. Other body cells die and are (12) by new cells. In an aging person the (13) cells may not be as able to develop or as capable (14) growth as those of a young person. Another (15) in aging may be changes within the cells themselves. Some of the protein chemicals in cells are known to change with age and become less elastic. This is why the skin of old people wrinkles and (16) loose. This is also the reason old people (17) in height. There may be other more important chemical (18) in the cells. Some complex cell chemical, such as DNA and RNA, store and pass (19) information that the cells need. Aging may affect this (20) and change the information-carrying molecules so that they do not transmit the information as well.
No one can deny that pesticides have improved the ability of farmers to bring their crops to market. (1) pesticides, farmers no longer have to worry that they will lose an entire crop (2) an army of cut worms(毛虫)or fruit flies. (3) , Americans can rely on a large and varied food supply. However, we Americans need to become more (4) about the effects those pesticides on our food. More (5) , we need to think about what new (6) is necessary to protect ourselves from a (7) too rich in pesticide residue. If we don’t demand greater (8) on pesticide use, we may be surprised, dismayed, and (9) horrified by the consequence of its use. On the most obvious level, farm workers who continue to use the pesticides (10) their present rate will be (11) serious disease. It’s no (12) that farmers (13) to herbicides: have a six times greater risk of getting cancer. (14) , children who live in homes where pesticides are used have an increased chance of getting childhood leukemia (白血病). But the farmers are not the only ones (15) risk. Consumers may also suffer serious side effects from daily (16) of foods tainted (污染) by pesticides. Although scientists have yet to prove the link (17) , they are concerned that pesticide use may be one reason for the starting increase in various forms of cancer like breast and colon (结肠) cancers. We need new legislating that (18) stricter standards governing pesticide residues in food. Much of the current legislation is based on ignorance. Simply (19) , we allow high levels of carcinogens (致癌物) in our food because we don’t know for sure that they do cause cancer in humans. Yet, why should we take the risk If there’s a chance that a pesticide causes cancer, then it should be (20) from use.
Most Americans spend far more of their leisure time on the mass media than people in any other countries. (1) , most of us hear, see, (2) read some of the media while (3) other activities. Thus an (4) large number of our waking hours are spent with the mass media. (5) all the media, television is clearly (6) , with newspapers a close second, as a (7) of news and other information. Our (8) to all media is important, (9) , because all of them contribute materials for the construction of that world in our heads. For most people, increased use of one medium does not (10) use of another. In fact, in certain cases, and especially for certain purposes, the more one uses one medium, the more (11) one is to use others. There are various (12) that can cause you to (13) yourself to the media (14) , avoiding much of the material with which you disagree. Some of that selective exposure is probably (15) the psychological pressure you feel to avoid the discomfort caused by confrontation with facts and ideas contrary to your beliefs, attitudes, or behavior. However, some selective exposure is not due to the pressure for consistency but to other factors, such as your age, education, and even the area in which you live and the people with whom you associate. Quite a few sorts of factors that (16) your media experience is the social context of exposure: whether you are alone or with others when you are exposed to a medium; whether you are at home, at the office, in a theater, and so on. These contexts are as much as a (17) part of the message you will (18) as film image on the screen or words on the page. In addition, that social context affects-both directly and indirectly-the media (19) to which you become exposed. New friends or colleagues get you interested in different things. Other members of the family often select media content (20) you would not have selected, and you become exposed to it. These various factors have so much influence on your media exposure that so little of that exposure is planned.
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