When we take a long nap during the day, it can be harder to fall asleep at night. How does the two-process model explain this?Group of answer choicesAlertness remains high at night because of the napNaps can change the underlying circadian rhythmSleep pressure has been reduced by the napThe sleep gate is closed

The two-process model of sleep regulation explains this phenomenon through the concept of sleep pressure. According to this model, two processes determine our sleep-wake cycle: the circadian process (Process C) and the homeostatic process (Process S).

Process C is our internal biological clock that regulates the timing of periods of sleepiness and wakefulness throughout the day. Meanwhile, Process S, or sleep pressure, builds up the longer we are awake and decreases during sleep.

When we take a long nap during the day, we reduce the sleep pressure (Process S). This means that by the time we go to bed at night, we may not have accumulated enough sleep pressure to feel sleepy. Therefore, it can be harder to fall asleep at night after taking a long nap during the day.

So, the correct answer is "Sleep pressure has been reduced by the nap".