阅读下面短文，从每小题所给的A、B、C、D四个选项中选出最佳选项。          

World Sleep Day organized by WASM since 2008, is on March 21 every year.The year 2021 marks the 14th World Sleep Day. The slogan for WSD 2021 is "Regular Sleep, Healthy Future." World Sleep Day is to celebrate thebenefits of good and healthy sleep. Researchers say that there are a lot of advantages if we always get enough sleep. We can be smarter, thinner and healthier. Also we can have better skin, better memories and longer lives. For our good life and work, it's necessary for us to realize the importance of sleep and try to have a good sleep.

How much sleep do we need? Adults need at least eight hours of sleep a night. Students under 14 need at least nine hours of sleep every night. However, about 80% of high school students don't get enough sleep because of their schoolwork or some bad habits. There is something you can do to have a good sleep. ▶Exercise more, but not right before bed. Early to bed, early to rise. ▶Drink a glass of milk before sleeping. Keep away from coffee, tea or chocolate at least 6 hours before bedtime. ▶Keep the bedroom between 16℃-19 ℃. ?Don't put computer, TV, and mobile phones in your bedroom.