题目内容：

         All of us eat every day, but most of us don’t understand nutrition. We often make mistakes in talking about good diet.

For example, many people think that foods such as rice, bread and potatoes will make one grow fat. In fact, these foods are very good to one’s health. They are good sources of many vitamins. And in comparison with steak and beef, they contain less amount of calories.

Some people don’t like canned(罐装的) or frozen vegetables, because they think fresh vegetables cooked at home are always better. This is again wrong. In fact, whether the vegetables are good or not depends more on how they are prepared. Overcooking, for example, destroys good qualities of vegetables. Vegetables cooked in too much water can lose a large amount of vitamins.

It is widely believed extra vitamins provide more energy. But taking more than the body needs doesn’t make it function better.

It is also wrong to say that vegetables grown in poor, worn-out soil are lower in vitamins than vegetables grown in rich soil. The vitamins in our foods are in the plants themselves. They don’t come from the soil. However, the minerals(矿物质) in a plant depend on the minerals in the soil.

In short, there are many false ideas about nutrition. We need to correct them.

46. This passage is mainly about_______.

A. nutrition                B. vitamins                C. vegetables            D. health

47. Rice, bread and potatoes do good to people’s health mainly because_______.

A. they make people fat                              B. there are lot of vitamins in them

C. they contain less amount of calories compared with steak and beef.

D. both B and C.

48. Why don’t some people like canned or frozen vegetables? Because______.

A. they think fresh vegetables contain less vitamins

B. they think fresh vegetables contain more vitamins than the canned or frozen ones

C. they don’t think the canned or frozen vegetables are fresh

D. they don’t think the canned or frozen vegetables taste as good as the fresh ones

49. Which of the following is true according to the passage?

A. Many people know almost everything about nutrition.

B. Food such as rice, bread and potatoes make people fat.

C. vegetables grown in poor worn-out soil may have the same amount of vitamins as vegetables grown in rich soil.

D. extra vitamins provide less energy.

50. The point of the passage is that______.

A. the minerals in a plant depend on the minerals in the soil

B. people make mistakes when talking about good diet

C. taking more vitamins than the body needs doesn’t make it function better

D. vegetables cooked in too much water can lose a large amount of vitamins