A、Because he is a politician. B、Because he is a businessman. C、Because he travels by air. D、Because he has to attend different m

Air travel is such an everyday experience these days. We are not surprised when we read about a politician having talks with the Japanese Prime Minister one day, attending a conference in Australia the following morning and having to be off at midday to sign a trade agreement in Bangkok. But frequent long-distance flying can be very tiring. The traveler begins to feel his brain is in one country, his digestion in another and his powers of concentration nowhere. In short, he hardly knows where he is.
    The fatigue we normally experience after a long journey is more intensely felt when we fly from east to west or the other way round because we cross time zones. Air travel is so quick nowadays that we can leave London after breakfast and be in New York in eight hours, yet what really disturbs us most is that when we arrive it is only lunch time but we have already had lunch on the plane and are expecting dinner.
    Doctors say that since air travelers are in no condition to work after crossing a number of time zones, they should go straight to bed on arrival. Airline pilots, in fact, whose experience is so obviously relevant that it ought to serve as a guide, often live by their own watches ignoring local time, and have breakfast at midnight if necessary. The less reason to worry about their health is because they are used to flying and are physically fit.