1.【2015·重庆】B
Imagine the first days in a new time zone. Slow to respond to the 28 , 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 29 jet lag（时差反应）.
Travelers have traditionally fought this 30 with sleeping pills or alcohol. There are actually healthier ways that can work just as 31.
