照片上各组织间的密度差异称为（） A.组织对比度 B.胶片对比度 C.照片对比度 D

Do you find getting up in the morning so difficult that it's 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 labor through your work you may say that you're “hot”. That's true. The time of day when you feel most energetic is when your cycle of body temperature is at its peak(高峰). For some people the peak comes before noon. 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.
小题1:If a person finds getting up early a problem, most probably________.

A．he is a lazy person

B．he refuses to follow his own energy cycle

C．he is not sure when his energy is low

D．he is at his peak in the afternoon or evening

小题2:Which of the following may lead to family quarrels according to the passage?

A．Unawareness of energy cycles.	B．Familiar monologues.
C．A change in a family member's energy cycle.
D．Attempts to control the energy cycle of other family members.

小题3:. If one wants to work more efficiently at his low point in the morning, he should________.

A．change his energy cycle	B．overcome his laziness
C．get up earlier than usual	D．go to bed earlier

小题4:Which of the following statements is NOT true?

A．Getting off to work with a minimum effort helps save one's energy.

B．Dr. Kleitman explains why people reach their peaks at different hours of day.

C．Habits help a person adapt to his own energy cycle.

D．Children have energy cycles, too.