完形填空 (共10小题；每小题2分，满分20分)
阅读下面短文，掌握其大意，然后从21—30各题所给的A、B、C和D项中，选出最佳选项，并在答题卡上将该项涂黑。
Do you find getting up in the morning so difficult that it’s painful? This might be called  21 , but Dr. Kleitman has a new  22 . He has proved that everyone has a   23   energy cycle. During the hours when you   24   through your work you may say that you’re “hot”. That’s  25  . The time of day when you feel most   26   is when your cycle of body temperature is at its peak. For some people the  27   comes during the forenoon. For others it comes in the afternoon or evening. No one has discovered why this is so, but it  28   such familiar monologues 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   29 . Much family quarrelling ends when husbands and wives  30  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.
21. A. patience    B. laziness      C. sadness       D. comfort
22. A. discovery   B. invention     C. explanation    D. statement
23. A. changing    B. increasing    C. full          D. daily
24. A. labour      B. get          C. go            D. look
25. A. honest      B. actual       C. true           D. real
26. A. pleasant     B. energetic    C. excited        D. comfortable
27. A. power      B. energy       C. peak           D. altitude
28. A. comes to    B. gets to       C. leads to        D. refers to
29. A. morning    B. afternoon     C. evening        D. noon
30. A. realize      B. recognize     C. memorize      D. see