Two years ago. the incidence of nearsightedness was 20 to 30 percent among primary school students in China, 40 to 50 percent among junior middle school students, 50 to 60 percent among senior middle...
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Two years ago. the incidence of nearsightedness was 20 to 30 percent among primary school students in China, 40 to 50 percent among junior middle school students, 50 to 60 percent among senior middle...