Do you find getting up in the morning so difficult that it is painful? This might be called laziness, but Dr. Kleitman has a new explanation. He has proved that everyone has a daily energy cycle.

　　During the hours when you labour through your work you may say that you are “hot”. That's true. The time of day when you feel most energetic is when your cycle of body temperature is at its peak. For some people the peak comes during the forenoon. For others it comes in the afternoon or evening. No one has discovered why this is so, but it leads to such familiar monologues（自言自语）as: “Get up, John! You'll be late for work again!” The possible explanation to the trouble is that John is at his temperature-and-energy peak in the evening. Much family quarrelling ends when husbands and wives realize what these energy cycles mean, and which cycle each member of the family has.

　　You can't change your energy cycle, but you can learn to make your life fit it better. Habit can help, Dr. Kleitman believes. Maybe you're sleepy in the evening but feel you must stay up late anyway. Counteract（对抗）your cycle to some extent by habitually staying up later than you want to. If your energy is low in the morning but you have an important job to do early in the day, rise before your usual hour. This won't change your cycle, but you'll get up steam（鼓起干劲）and work better at your low point.

　　Get off to a slow start which saves your energy. Get up with a leisurely yawn and stretch. Sit on the edge of the bed a minute before putting your feet on the floor. Avoid the troublesome search for clean clothes by laying them out the night before. Whenever possible, do routine work in the afternoon and save tasks requiring more energy or concentration for your sharper hours.

You are advised to rise with a yawn and stretch because it will ____.（　　）

• A.help to keep your energy for the day's work
• B.help you to control your temper early in the day
• C.enable you to concentrate on your routine work
• D.keep your energy cycle under control all day