例句：
Exercise tones up your body.
运动强健身体。
Riding a bike is great exercise.
骑自行车是很好的'锻炼。
Swimming is good exercise.
游泳是有益的运动。
How often do you exercise?
你多长时间锻炼一次？
Swimming is a good form of exercise.
游泳是很好的锻炼方式。
