单选题 People who work night shifts are constantly fighting against an “internal clock” in their bodies. Quite often the clock tells them to sleep when their job requires them to remain fully awake. It's no wonder that more accidents happen during night shifts than at any other time. Light therapy(光照治疗法)with a bright light box can help night-shift workers adjust their internal clock. However, many doctors recommend careful planning to help improve sleep patterns For example, night-shift workers often find it difficult to sleep in the morning when they get off work because the body's natural rhythm(节律)fights back, no matter how tired they are. Some experts recommend that night-shift workers schedule two smaller sleep periods-one in the morning after work, and another longer one in the afternoon, closer to when the body would naturally need to sleep. It’s also helpful to ask friends and family to cooperate by avoiding visits and phone calls during the time when you are sleeping.

单选题 Night-shift workers are those who ______．
A．have to pay on their internal clock B．need to re-adjust their clock
C．fall asleep late at night D．have to work at night

【正确答案】 D

【答案解析】[解析] 根据短文前两句可知，“night-shift workers“就是那些值夜班的工人。

单选题 In order to remain fully awake at work，people working night shifts should ______.
A．have longer sleep periods after work B．make the light darker than usual
C．try to reset their “internal clock” D．pay more attention to their work

【正确答案】 C

【答案解析】[解析] 短文第四句提到一种光照治疗法，其实就是为了调节他们的内部时钟。“Light therapy(光照治疗法)with a bright light box can help night-shift workers adjust their internal clock. ”

单选题 Many doctors think it is helpful for night-shift workers ______．
A．to sleep with a bright light on
B．to plan sleep patterns carefully
C．to avoid being disturbed at work
D．to sleep for a long time after work

【正确答案】 B

【答案解析】[解析] 短文第五句“However, many doctors recommend careful planning to help improve sleep patterns”，接着说明安排睡眠模式。

单选题 Night-shift workers often find it difficult to sleep in the morning because ______．
A．their internal clock will not allow them to
B．they are often disturbed by morning visits
C．they are not trying hard enough to do so
D．they are too tired to go to sleep well

【正确答案】 A

【答案解析】[解析] 为什么值夜班的工人在早上难以入睡?从短文中的举例说明怎样安排睡眠模式可知，原因在于人体内的自然节律，也就是内部时钟。

单选题 According to the passage, some doctors recommend that night-shift workers should ______.
A．have frequent visits and phone calls B．improve their family relationship
C．have two smaller sleep periods D．rely mainly on light therapy

【正确答案】 C

【答案解析】[解析] 短文倒数第二句：“Some experts recommend that night-shift workers schedule two smaller sleep periods…”