Nowadays, air travel is very【21】. We are not surprised when we watch on TV that a politici

an has talked with French President in Paris and attended a meeting in Beijing on the same day.【22】, if a person takes long-distance flying frequently, he can be so tired that he maybe feel his brain is in one country, his【23】in another.【24】, he【25】knows where he is.

When we fly from east to west or【26】versa, the【27】we experience after taking a long distance flying is【28】, because we cross time zones. According to doctors, air travelers, after crossing several time zones, are in no【29】to go to work, and they should go【30】to bed【31】arrival.

As to airline pilots who often live【32】their own watches and ignore local time, there is no need for them to worry about their health although they sometimes have breakfast at midnight, because they are used to【33】and are【34】fit.

Many businessmen like long-distance flights, thinking they are【35】to have been chosen and they are out for promotion. They are lucky if the company follows the doctor' s advice and allow them to rest for a day or two【36】working. However, sometimes the manager is so energetic that he believes everyone is【37】to be as fit as he is. Since he has never felt【38】after flying himself, the work he assigns is so【39】that the employee is too【40】to carry the work out satisfactorily. That is disastrous for the employee' s health and the company' s reputation.

(21)

A．ordinary

B．common

C．plain

D．usual