Passage I 

Low in calories and fat, the banana is a perfect example of a flavorful food that is exceptionally good for you. It contains a number of minerals, notably potassium (钾) , one of the body’ s most important elements. Potassium provides a counterbalancing action with sodium (钠) and is directly connected to proper fluid balance and overall muscle tone. A potassium shortage can lead to weakness, insomnia (失眠) , even an irregular heart rate. Keep up your natural potassium supply with a banana a day, sliced on cereal (谷物) , wrapped into pancakes or frozen on a stick.