Most people who travel long distances complain of jetlag (飞行时差反应) Jetlag makes business travelers less productive and more prone【C1】______ making mistakes. It is actually caused by.【C2】______ of your 'body clock' --a small cluster of brain cells that controls the timing of biological【C3】______ . The body clock is designed for a【C4】______ rhythm of daylight and darkness, so that it is thrown out of balance when it【C5】______ day light and darkness at the 'wrong' times in a new time zone. The【C6】______ of jetlag often persist for days【C7】______ the internal body clock slowly adjusts to the new time zone. Now a new anti-jetlag system is【C8】______ that is based on proven【C9】______ pioneering scientific research. Dr. Martin Moore-Ede has【C10】______ a practical strategy to adjust the body clock much sooner to the new time zone【C11】______ controlled exposure to bright light. The time zone shift is easy to accomplish and eliminates【C12】______ of the discomfort of jetlag. A successful time zone shift depends on knowing the exact times to either【C13】______ or avoid bright light. Exposure to light at the wrong time can actually make jetlag worse. The proper schedule【C14】______ light exposure depends a great deal on【C15】______ travel plans. Data on a specific flight itinerary (旅行路线) and the individual's sleep【C16】______ are used to produce a Trip Guide with【C17】______ on exactly when to be exposed to bright light. When the Trip Guide calls【C18】______ bright light you should spend time outdoors if possible. If it is dark outside, or the weather is bad,【C19】______ you are on an airplane, you can use a special light device to provide the necessary light【C20】______ for a range of activities such as reading, watching TV or working. 【C1】