题目内容：
根据以下资料，回答题： Nowadays，air travel is very 21．We are not surprised when we watch on TV that a politician 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___ 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．
A．ordinary
B．common
C．plain
D．usual
参考答案：【答案仅供学习，请勿对照自行用药等】
答案解析：