问题
单项选择题
碳素钢按其用途可分为碳素结构钢和碳素（）钢。
A、工具
B、模具
C、合金
D、高速钢
答案
参考答案：A
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碳素钢按其用途可分为碳素结构钢和碳素（）钢。
A、工具
B、模具
C、合金
D、高速钢
参考答案：A
| The United States government publishes guidelines for appropriate nutrient intakes. These are known as the Recommended Dietary Allowances (RDAs) and are updated regularly based on new research in nutrition. RDAs are suggested amounts of calories, protein, and some minerals and vitamins for an adequate diet. For other dietary substances, specific goals must await further research. However, for the U.S. population as a whole, increasing starch and fiber in one’s diet and reducing calories (primarily from fats. sugar, and alcohol) is sensible. These suggestions are especially appropriate for people who have other factors for chronic diseases due to family history of obesity, premature heart disease, diabetes, high blood pressure, and high blood cholesterol, or for those who use tobacco. Snacks can furnish about one-fourth of the calorie requirements among teenagers. Those snacks should also provide much of the day’s allowances for protein, minerals, and vitamins. Sandwiches, fruit, and milk make good snacks for active teenagers. Food from the food pyramid may be part of any meal. A grilled cheese sandwich or a bowl of whole-grain cereal is just as nutritious in the morning as it is at noon. In addition, a good breakfast consists of any foods that supply about one-fourth of the necessary nutrients for the day. |
The reduction of calories in the diet is particularly good for people who suffer from ______.
A．obesity
B．premature heart disease and diabetes
C．high blood pressure and cholesterol levels
D．all of the above