Meat and vegetables are measured in grams and kilograms. Milk and other liquid foods are measured in liters and milliliters. These units only measure quantity; they do not measure the value of the food to the body. The unit which measures the quality or value of food is the "calorie". A calorie is the amount of heat given off by food when it burns. This measurement tells how much energy a certain food has when it is completely used by the body.
Our bodies use varying amounts of calories. The more exercise we take, the more calories we burn. If we eat food which contains more calories than we use up, then it is possible that we would increase in weight. In order to avoid becoming overweight it is advisable to eat a balanced diet and not eat too many foods that have a high calorie rating. The table below gives you some idea of the number of calories in food.
To keep the calorie intake (纳入) down, it is better to eat______.

A. chocolate
B. meat pie
C. fruit
D. apple pie