Few things feel more like home than a warm bed on a winter morning. Don’t feel bad. You’re not alone in not wanting to leave it. Here’s what’s happening inside you and what you can do about it.

To start with, your vitamin(维生素) D levels are low. Vitamin D plays many roles in the body. Vitamin D levels drop because of shorter daylight hours and less powerful sun rays(光线). The shortage of Vitamin D can affect sleep, so you can’t wake up in the morning easily. Secondly, your melatonin(褪黑激素) levels are high. An increase in melatonin sends you off to sleep at night. Melatonin is produced for a longer time in winter when nights are long than in summer when nights are short. What’s more, researchers discovered cold temperatures can make your waking up hard, too. There are ways you can use to wake up early feeling refreshed.

Try getting more vitamin D. The first thing you can do to wake up earlier is to fight the shortage of Vitamin D. How? Try to get more sunshine. If the cold weather prevents you going outside, you can enjoy the sunshine next to an open window for five minutes. Lighting up your room in the mornings is the second thing you can do. Opening your bedroom lights in the morning is about more than making you too uncomfortable to keep sleeping. The body stops melatonin production when it starts to sense light, which makes you feel less tired. You can also put your heating on a timer. Then, increase the temperature about an hour before you want to wake up.

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1. What does the underlined word “affect” mean?（词义猜测）

A    Polish.

B    Boil.

C    Influence.

D    Divide.