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. 2.What makes it harder to fall asleep in bed after a long nap in sofa?（推理判断）

A    Alertness from activities.

B    Sleep cycle disruption.

C    Reduced sleep drive.

D    Uncomfortable bed.