（1）自行车的轮胎上，有许多花纹，其目的是 其轮胎属于 材料（填“有机合成材料”、“金属材料”或“无机材料”）。
（2）甲工厂排放的废水中含有稀硫酸，乙工厂的废液含有烧碱，为处理废液，可将两
个工厂的废液按一定比例混合。写出发生的化学方程式为 。
（1）使接触面变粗糙，增大摩擦力 有机合成材料
（2）2NaOH＋H2SO4＝Na2SO4＋2H2O
题目分析：合成材料包括塑料、合成纤维和合成橡胶；酸与碱发生的是中和反应，生成的是盐和水。
Passage Three
| 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 and also cause unpleasant side effects in some people. So it’s 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 (肠道) "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 fit 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 (类胡萝卜素), 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. |
What is a possible negative effect of olestra according to some critics
A．It may increase the risk of cancer.
B．It may impair the digestive system.
C．It may spoil the consumers’ appetite.
D．It may affect the overall fat intake.