阅读下面材料,从每小题所给的A、B、C、D四个选项中选出最佳选项。
Do you play with your phone before bedtime? According to a US study, looking at screens at night can cause us to sleep badly.
In the evening, our bodies make melatonin (褪黑素),Melatonin helps us feel sleepy and relaxed. It's an important part of our sleep cycle (周期). However, our electronic screens stop that cycle from working normally. That's because phones, computers and TVs make blue light. Blue light stops our bodies from making melatonin. Even just a little bit of blue light can make a difference. Eight minutes of blue light can keep our brain (大脑) "awake”for another hour, according to the study. Even if we fall asleep, we may have lots of dreams. Our brain won't have a good rest.
It's even worse if you play an exciting game before going to bed. Games make our hearts beat faster, so we have a harder time falling asleep. Then, when we fall asleep, we don't get enough "deep sleep". So next day we will feel very tired.
Use these following tips to get a good night's sleep.
★Have a relaxing habit every night. Take a warm shower, or read a book, and then you can relax yourself.
★Sleep in a dark, quiet room and the room is not too warm or too cold. This can help you fall fast asleep.
★Count sheep. It's the oldest way, but it can really work! So if you can't get to sleep, try this one.
★Don't eat a big meal or have caffeine, but you can drink some milk. Don't run around or exercise for three hours before bedtime.