2016年西北大學(xué)考博英語真題

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Imagine eating everything delicious you want—with none of the fat. That would be great, wouldn’ t it? New “fake fat" products appeared on store shelves in the United States recently, but not everyone is happy about it. Makers of the products, which contain a compound called olestra, say food manufacturers

can now eliminate fat from certain foods. Critics, however, say the new compound can rob the body of essential vitamins and nutrients （營養(yǎng)物）and can also cause unpleasant side effects in some people. So it’s up to decide whether the new fat-free products taste good enough to keep eating. Chemists discovered olestra in the late 1960s, when they were searching for a fat that could be digested by infants more easily. Instead of finding the desired fat, the researchers created a fat that can51 be digested at all.

Normally, special chemicals in the intestines （腸）“grab” molecules of regular fat and break them down so they can be used by the body. A molecule of regular fat is made up of three molecules of substances called fatty acids. The fatty acids are absorbed by the intestines and bring with them the essential vitamins A, D, E, and K. When fat molecules are present in the intestines with any of those vitamins, the vitamins attach to the molecules and are carried into the bloodstream. Olestra, which is made from six to eight molecules of fatty acids, is too large for the intestines to absorb. It just slides through the intestines without being broken down. Manufacturers say it，s that ability to slide unchanged through the intestines that make olestra as valuable as a fat substitute. It provides consumers with the taste of regular fat without any bad effects on the body. But critics say olestra can prevent vitamins A, D, E, and K from being absorbed. It can also prevent the absorption of carotenoids （類胡蘿卜素），compounds that may reduce the risk of cancer, heart disease, etc.. Manufacturers are adding vitamins A, D, E, and K as well as carotenoids to their products now. Even so some nutritionists are still concerned that people might eat unlimited amounts of food made with the fat substitute without worrying about how many calories they are consuming.

76. We learn from the passage that olestra is a substance that .

A. contains plenty of nutrients

B.renders foods calorie-free while retaining their vitamins

C. makes foods easily digestible

D. makes foods fat-free while keeping them delicious

77. The result of the search for an easily digestible fat turned out to be .

A. commercially useless B. just as anticipated

C. somewhat controversial D. quite unexpected

78. Which of the following is NOT true about the fatty acid?

A. The fatty acid is made up of three molecules of substances.

B.The fatty acid can be absorbed by the intestines.

C. The fatty acid brings the essential vitamins A, D, E and K to the intestines.

D. Olestra is made from six to eight molecules of fatty acids.

79. Olestra is different from ordinary fats in that .

A. it passes through the intestines without being absorbed

B. it facilitates the absorption of vitamins by the body

C. it helps reduce the incidence of heart disease

D. it prevents excessive intake of vitamins

80. Why are nutritionists concerned about adding vitamins to olestra?

A. It may lead to the over-consumption of vitamins.

B.People may be induced to eat more than is necessary.

C. The function of the intestines may be weakened.

D. It may trigger a new wave of fake food production.

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