Excessive calories from sugar can contribute to weight problems,and sugar is also well known for its ability to promote teeth __1__ decay.Too many calories from fat have also taken their toll from the __2__ public's health. In 1988, the U.S surgeon general issued a report linking high level of fat intake to an increased risk for obesity.Obesity is a risk factor for high bloody pressure, stroke, and __3__ diabetes. Research has also shown a relationship between high levels of fat in the diet and cancer. In addiction, scientists have linked some types of fat to high blood cholesterol level,which must lead to heart disease. Such reports have prompted __4__ health experts and nutritionists to recommend that adults and children over age 2 not only watch their sugar intake but also to limit their fat intake to a maximum of 30% of their __5__ complete calories. This has encouraged many people to turn __6__ to products made with fat and sugar substitutes.Low-calorie sugar substitutes have been around for decades,but the recent trend in eating "light" has created a boom in this branch of food-technology research. Today, food chemists are seeking for better substitutes by modifying existing foods, __7__ searching for new compounds in nature, and concoct entirely __8__ new substances. But the research process is complicated by our incomplete understanding of how the human body interacts with the chemicals we eat.For example, scientists do not already know exactly why some __9__ substances taste sweet. Other questions involve the safe and __10__ usefulness of artificial fats and sweeteners.
答案：
1.teeth--tooth。名词直接作前置修饰语的时候，应该用单数形式。
2.（toll）from--on。take one's toll on somebody/ something 的意思是“使得……受损失、对……产生不良影响”，如The terrible weather took its toll on my health。恶劣的天气对我的健康产生（不良）影响。
3.bloody--blood。bloody和blood都可以作为定语修饰名词，但是bloody的意思是“血腥的”。
4.must--may/can。这里上下文并没有必然的联系，所以用must是不恰当的，应该用比较弱的推测语气。
5.to（limit）--/。but also和前面的not only 构成并列结构，所以动词应该是不带to的不定式。
6.complete--total。原文的意思是“摄入的卡路里的总量”，表示数量上的总数应该用total，complete侧重表示 程度，组成部分的完整性。
7.for--/。seek是及物动词，直接跟宾语，要和look for 区分开来。
8. concoct--concocting。动词concoct通过连词and和前面的modifying、searching并列，所以应该是-ing分词。
9.already--yet。这是一个否定句，所以应该用yet。
10.safe--safety。safe是形容词，它作为名词的意思是“保险箱”，所以应该改成safety。
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