After a long day, you flop onto the sofa and find yourself dozing off while watching TV. Then a loved one nudges you awake and reminds you to go to sleep — in bed. But when you get there, you find to your frustration that you’re wide awake. Why?

Sleep pressure is one reason why you fall asleep on the sofa. This refers to the strength of the biological drive for sleep. The longer you’ve been awake, the greater the sleep pressure. Your body’s circadian rhythm is another factor. This tells you to be awake during the day and to sleep at night. Your environment will also impact how likely it is you fall asleep. You might have just eaten a meal, your very comfortable sofa is in a warm room, with dim lighting and maybe a TV program in the background. For many people, this environment is perfect for falling asleep. 

If you’ve had a nap on the sofa before heading to bed, your sleep pressure is likely much lower than it was before your nap. Instead of having more than 16 hours of wakefulness behind you, you’ve just woken up and therefore have less sleep pressure. This can make it much harder to fall asleep in bed. If you just fell asleep on the sofa for five minutes, you might not have too much trouble getting to sleep in bed. This is because a nap that short is unlikely to reduce your sleep pressure very much. But if you were asleep for an hour, it might be a different story.

Your sleep cycles might also be working against you. If you wake up during deep sleep, you’re likely to feel groggy, which might actually help you fall back asleep quickly when you get to bed. However, if you wake up during light sleep, you’re already closer to a state of wakefulness, making it much harder to fall asleep again. The activities you might do when you get up from the sofa — like turning on bright lights or brushing your teeth — can also make you feel more alert and make it harder to sleep when you get to bed. 

1.1.What does the term “circadian rhythm” refer to in the passage?

A Sleep-wake cycle.

B Deep sleep phase.

C Environmental cues.

D Meal times.

解析：选A。A词义猜测题。文章第二段提到“Your body circadian rhythm is another factor. This tells you to be awake during the day and to sleep at night. ” 它指示人们白天清醒、夜晚睡眠，即昼夜节律。选项A“Sleep-wake cycle”准确反映了这一概念，其他选项（深睡阶段、环境线索或进餐时间）与词义不符。故选A。

2.2.What makes it harder to fall asleep in bed after a long nap in sofa?

A Alertness from activities.

B Sleep cycle disruption.

C Reduced sleep drive.

D Uncomfortable bed.

解析：选C。C推理判断题。文章第三段指出“If you’ve had a nap on the sofa before heading to bed, your sleep pressure is likely much lower than it was before your nap.”上床睡觉前在沙发上的小睡会降低睡眠压力，从而减少睡眠压力，导致在床上更难入睡。选项C“Reduced sleep drive”正确推理了这一原因。其他选项（睡眠周期中断、活动导致的警觉或不舒适的床）虽可能与睡眠困难相关，但并非小睡后的主要原因。故选C。

3.3. How does a short nap (e.g., 5 minutes) affect sleep pressure according to the passage?

A Reduces it greatly.

B Hardly reduces it.

C Increases it slightly.

D Disrupts it completely.

解析：选B。B细节理解题。第三段末尾提到“If you just fell asleep on the sofa for five minutes, you might not have too much trouble getting to sleep in bed. This is because a nap that short is unlikely to reduce your sleep pressure very much. ”一个五分钟的短小憩不太可能大幅降低你的睡眠压力。选项B “Hardly reduces it”（几乎不减少它）是对原文的同义转述。其他选项均与原文事实不符。故选B。

4.4.Which makes it easier for you to fall back asleep?

A Brushing your teeth.

B Turning on bright lights.

C Waking during light sleep.

D Waking during deep sleep.

解析：选D。D细节理解题。第四段提到“If you wake up during deep sleep, you’re likely to feel groggy, which might actually help you fall back asleep quickly when you get to bed.”如果你从深睡中醒来，可能会感到昏昏沉沉，这种状态实际上可能会帮助你在躺下后更快地再次入睡。其他三项均会让你更难再次入睡。故选D。