Imagine the first days in a new time zone. Slow to respond to the          , your body clock is confused. You’re sleepy all day, but when it’s time for bed, you can hardly fall asleep. Obviously you are    jet lag（时差反应）.
Travelers have traditionally fought this          with sleeping pills or alcohol. There are actually healthier ways that can work just as 31.
For example, the moment you get on the airplane, start           your biological block to the destination’s time. If it’s daytime in your destination, try to stay           . Walking around the cabin（客舱） can be of help. When it’s nighttime, try to sleep. In that case, eat before the flight,          an empty stomach will prevent you from sleeping. These tips will help you start a new        of sleep and wakefulness.

A．flight B．change C．demand D．climate

A．suffering from B．working on C．looking into D．leading to

A．danger B．problem C．waste D．fear

A．briefly B．slowly C．suddenly D．effectively

A．checking B．sending C．adjusting D．stopping

A．awake B．alone C．hungry D．calm

A．though B．so C．whole D．or

A．understanding B．cycle C．research D．trend