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 that the new compound can rob the body of essential vitamins and nutrients and can also cause unpleasant side effects in some people. So it is up to consumers 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 can't be digested at all. Normally, special chemicals in the intestines " 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 makes olestra so 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, 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.

单选题 We learn from the passage that olestra is a substance that______.

单选题 The result of the search for an easily digestible fat turned out to be______.

【正确答案】 D

【答案解析】解析：推理题。根据文章第三段可知，“olestra”是化学家在20世纪60年代末发现的，他们的目的是为了寻找一种婴儿容易消化的脂肪，但是在这个过程中，他们偶然制造出一种不被消化的脂肪，即“olestra”。根据“instead of finding the desired fat，”可以推断出 “olestra”的发现是偶然的。故答案为D(意料之外的)。

单选题 Olestra is different from ordinary fats in that______.

【正确答案】 A

【答案解析】解析：细节题。根据文章第四段可知，普通的脂肪只含有三个脂肪酸分子(three molecules of substances called fatty acids)。根据文章第五段可知，这些脂肪酸分子在经过肠道时被吸收而且带来了重要的维生素A、D、E和K。再根据第六段的首句“Olestra，which is made from six to eight molecules of fatty acids，is too large for the intestines to absorb．”可知， “olestra”是由6到8个脂肪酸分子组成，因为体积太大而不能被肠道吸收。故答案为A。

单选题 What is a possible effect of olestra according to some critics?

【正确答案】 C

【答案解析】解析：推理题。根据文章第六段倒数第二句中的“But critics say olestra can prevent vitamins A，D，E and K from being absorbed．It can also prevent the absorption of carotenoids， compounds that may reduce the risk of cancer，heart disease，etc．”可知，一些批评家认为 olestra阻止人体吸收维生素A、D、E、K和类胡萝卜素(carotenoids)，而类胡萝卜素却是一种能减少癌症及心脏病发病率的化合物。所以答案为C。

单选题 Why are nutritionists concerned about adding vitamins to olestra?

【正确答案】 B

【答案解析】解析：细节题。根据文章最后一段中的“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．”可知，一些营养学家担心这样一来，人们也许会不加限制地享用由代脂肪制成的食品，从而摄取了更多的热量。所以答案为B。