题目内容
A．People think too much of their appearance.B．There is not a sure way of losing weight
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Women live longer than men because they are spoiled for choice. That is the startling conclusion of an international group of scientists who say they have found the cause of female longevity.
They say females have two separate cell lines in their bodies, while men have only one. Women in old age can "choose" the more robust (强壮的) of these lines and survive for many more years.
Why there should be such a persistent cross-cultural gap between the life spans of the sexes has baffled scientists until now. In a paper in the journal Blood, and reported in the current issue of New Scientist, researchers at Odense University in Denmark and Ulleval University Hospital in Norway point to a key difference in the sex-determining chromosomes (染色体) found in the cells of men and women.
Every cell in a woman's body has two X chromosomes, one inherited from her mother and the other from her father. In each cell, one of these two X chromosomes is switched off. This means that a woman is a mosaic (混合体) of two cell lines: one derived from her father's X chromosome, the other from her mother's. By contrast, every cell in a man's body has an X and a Y chromosome, neither of which is turned off. He has only one cell line. This difference could be crucial in determining the long-term health of men and women, scientists concluded, and so they decided to examine cells taken from young women.
They found an even division between their two different lines. However, when they looked at elderly females they found their bodies now favoured one set of cells at the expense of the other line. "This suggests that one of the cell lines is 'better' than the other," say the researchers. In other words, women's bodies may select the more vigorous of the two cell lines and allow it to predominate the twilight of their years, giving them a crucial advantage over men, who have no chance of choosing the healthier of two sets of cells.
Women enjoy a longer life than men because______.
A．Some old form. of ideal world.B．Adventures in ocean.C．Predicting development in tech
A．The amount of cloud covering.B．The wind conditions.C．The amount of snow.D．The temper
Section B
Directions: In this section, you will hear 3 short passages. At the end of each passage, you will hear some questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A, B, C and D.
听力原文： About 70 million Americans are trying to lose weight. That is almost I out of every 3 people in the United States. Some people are on a diet. This means they eat less of cetrain foods, especially fats and sugars. Other people exercise with special equipment, take medicine, or even have operation. Ix) sing weight is hard work, and it can also cost a lot of money. But why do so many people in the United States want to lose weight？
Many people in the United States worry about not looking young and pleasant. For many people, lot king good means being thin. Other people worry about their health. Many doctors say being overweight is not healthy. But. are Americans really fat？ Almost 30 million people in America weigh at least 20 percent more than their proper weight. In fact, the Unites States is the most overweight country in the world.
(27)
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