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Which of the following is not a possible damage by UV radiation？
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Population Densities
The average population density (密度) of the World is47 persons per square mile. Continental densities range from no permanent inhabitants in Antarctica to 211 per square mile in Europe. In the western hemisphere, population densities range from about 4 per square mile in Canada to 675 per square mile in Puerto Rico. In Europe the range is from 4 per square mile in Iceland to 831 per square mile in the Netherlands.
Within countries there are wide variations of population densities. For example, in Egypt, the average is 55 persons per square mile, but 1,300 person inhabit each square mile in settled portions where the land is arable (适合耕种的).
High population densities generally occur in regions of developed industrialization, such as the Netherlands, Belgium, and Great Britain, or where lands are intensively used for agriculture, as in Puerto Rico and Java.Low average population densities are characteristic of most Underdeveloped countries.
Low density of population is generally associated 'with a relatively low percentage of cultivated land.This generally results from poor quality lands. It may also be due to natural obstacles to cultivation, such as deserts, mountains, or malaria-infested (疟疾横行) jungles; to land uses other than cultivation, as pasture and forested land; to primitive methods that limit cultivation; to social obstacles
More economically advanced countries of low population density have, as a rule, large proportions of their populations living :in urban areas. Their rural population densities are usually very low. Poorly developed countries of correspondingly low population density, on the other hand, often have a concentration of rural population living on arable land, which is as great as the rural concentration found in the most densely populated industrial countries.
Which of the following area has the highest average population density？
Poorly developed countries of low population density may have
It is physically impossible for a well-educated, intellectual(理性的), or brave man to make money the chief of his thoughts; as physically impossible as it is for him to make his dinner the principal object of them. All healthy people like their dinner, but their dinner is not the main object of their lives. So all healthy-minded people like making money but the main object of their lives is not money; it is something better than money.
A good soldier, for instance, mainly wishes to do his fighting well. He is glad for his pay very properly so, and justly grumbles (抱怨) when you keep him ten months without it; still his main motion of his life is to win battles, not to be paid for winning them.
So of doctors. They like fees no doubt-ought to like them; yet if they are brave and well-educated, the entire object of their lives is not fees. They, on the whole, desire to cure the sick, and they are good doctors, and the choices were fairly put to them would rather cure their patients and lose their fees than kill him and get it. And so with all other brave and rightly trained men, their work is first, their fee second, very important always, but still second.
The main idea of the text is that _______.
Many cities around the world today are heavily polluted. Careless methods of production and lack of consumer demand for environment(环境) friendly products have contributed to the pollution problem. One result is that millions of tons of glass, paper, plastic, and metal containers are produced, and these are difficult to get rid of.
However, today more and more consumers are choosing "green" and demanding that the products they buy should be safe for the environment. Before they buy a product, they ask questions like these: "Will this shampoo damage the environment？ .... Can this metal container be reused or can it only be used once？"
A recent study showed that two out of five adults now consider the environmental safety of a product before they buy it. This means that companies must now change the way they make ad sell their products to make sure that they are "green", that is, friendly to the environment.
Only a few years ago, it was impossible to find green products in supermarkets, but now there are hundreds. Some supermarket products carry labels (标签) to show that the product is green. Some companies have made the manufacturing(生产) of clean and safe products their main selling point and emphasize it in their advertising.
The concern for a safer and cleaner environment is making companies rethink how they do business. No longer will the public accept the old attitude of "Buy it, use, it, throw it away, and forget it." The public pressure it on, and gradually business is cleaning up its act.
It becomes clear from the text that the driving force (动力)behind green products is ________.
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