If you need glasses to read this, you are among the majority of Chinese students. That's because most students in China are short-sighted which means they can only see things close up and distant things will be _ . Four-fifths of high school students wear glasses and now more and more children in primary school need glasses, too. This epidemic of poor eyesight has two very simple causes: too much time spent indoors studying and too little time spent outdoors playing. Reading and writing for hours and hours, sometimes in poorly lighted rooms, causes eyesight to weaken. But students have to do this because there is so much pressure on them to succeed in school. And because they spend so much time indoors at school and at home, they have less time to spend outdoors enjoying the sun. The sun, as a consequence, is important in developing good eyesight. Exposure to daylight releases a chemical in the eyes that prevents, or at least delays, short-sightedness. According to a study by Ian Morgan of Australian National University, Australian children and Chinese children have the same level of eyesight before they start school, but once they enter primary school, Chinese children only spend about an hour a day outside, while Australian children spend three to four hours each day in the sunshine. The result is that while about 40 percent of Chinese primary school students need glasses, only three percent of Australian children do. Wearing glasses may not seem like a big deal. For some, wearing glasses can even be an opportunity to make a fashion statement. But poor eyesight at a young age can have serious long term consequences. As you get older, your eyesight can worsen and lead to things like macular degeneration , a condition of the eyes for which there is no cure and which can eventually lead to blindness. With all that in mind, don't you think it's time to give your eyes a break? Try spending a little less time inside and go for a walk in the park, instead. It's the healthy thing to do and your eyes will thank you for it. It can be inferred from the passage that _ is to blame for the poor eyesight of Chinese children. A) the ever-worsening bad weather B) the ever-increasing burden of study C) the ever-decreasing sunny days D) the ever-decreasing period of study time
A:
B