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
名詞直接作前置修飾語的時候，應該用單數(shù)形式。
2.（toll）from--on
take one's toll on somebody/ something 的意思是“使得……受損失、對……產生不良影響”，如The terrible weather took its toll on my health。惡劣的天氣對我的健康產生（不良）影響。
3.bloody--blood
bloody和blood都可以作為定語修飾名詞，但是bloody的意思是“血腥的”。
4.must--may/can
這里上下文并沒有必然的聯(lián)系，所以用must是不恰當?shù)�，應該用比較弱的推測語氣。
5.to（limit）--/
but also和前面的not only 構成并列結構，所以動詞應該是不帶to的不定式。
6.complete--total
原文的意思是“攝入的卡路里的總量”，表示數(shù)量上的總數(shù)應該用total，complete側重表示 程度，組成部分的完整性。
7.for--/
seek是及物動詞，直接跟賓語，要和look for 區(qū)分開來。
8. concoct--concocting
動詞concoct通過連詞and和前面的modifying、searching并列，所以應該是-ing分詞。
9.already--yet
這是一個否定句，所以應該用yet。
10.safe--safety
safe是形容詞，它作為名詞的意思是“保險箱”，所以應該改成safety。