阅读下列材料，从A、B、C、D四个选项中选出最佳答案。
"I tell myself to sleep, but my eyes always stay open until 2 am, "said Li Pengfei, 29, who's working in Shenzhen. He has been having problems sleeping for over two years.
March 19 is World Sleep Day. Sleep is important because it gives our bodies time torecoverfrom the stress of living. But many people across China are losing sleep, according to the China Sleep Research Society (CSRS).
In China,38. 2 percent of the people have sleep disorder, well above the international level (水平) of 27 percent, CSRS reported.
This problem is especially serious among young people. According to a report by CSRS in2020, 69. 3 percent of young people in China usually sleep only 6. 4 hours each night. However, experts say adults should sleep 7 to 9 hours every night.
Pressure from work and school is the main reason for this. For Li Pengfei, heated competition is one of the things keeping him awake at night.
"We can be easily replaced(代替) by new people," he said. "Our jobs ask us to keep learning new things all the time. "
Another cause is the overuse of electronic devices(电子产品), such as smartphones and iPads. Many young people stay up late surfing the Internet and watching videos.
"With a typical 8:00 to 8:00 in the office, I always arrive home at 9 pm. I won't go to sleep right now. I need to do something different to relax myself. So a few hours of 'me time' is quite necessary," said Li Mingxin, 27, who works in Beijing.