单选题 The primary consideration in achieving a good balanced diet is not how much or how little we eat, but what we eat. Basically we need carbohydrates, protein, fat, vitamins and minerals, together with regular but not excessive exercise.
Carbohydrates are found in foods such as bread, potatoes and sugar. They are excellent energy producers, but if eaten to excess may be largely converted to fat and a reduction in the amount of carbohydrates or "starchy" foods is one of the obvious Ways to reduce weight, since most of us eat too much of them anyway.
According to the paragraphs, carbohydrates

• A. provide us with energy.
• B. are the main source of fat in the body.
• C. exist in all kinds of food.
• D. can make us feel goo