阅读理解。
    Imagine the first days in a new time zone. Slow to respond to the 1, your body clock is confused. You’re sleepy all day, but when it's time for bed, you can hardly fall asleep. Obviously you are2jet lag（时差反应）.

    Travelers have traditionally fought this 3 with sleeping pills or alcohol. There are actually healthier ways that can work just as 4.

    For example, the moment you get on the airplane, start 5 your biological block to the destination's time. If it's daytime in your destination, try to stay 6 . Walking around the cabin（客舱） can be of help. When it’s nighttime, try to sleep. In that case, eat before the flight, 7 an empty stomach will prevent you from sleeping. These tips will help you start a new 8of sleep and wakefulness.

一位美国历史学家这样总结道：在欧洲的海外扩张中最重要的人物不是哥伦布、达·伽马、麦哲伦，而是那些拥有资本的企业家们。对这一点最恰当的解释是（    ）