阅读短文，选择合适的选项。
Because of Covid-19, the schools are closed. But it does not stop(阻止) students from learning. The teachers become anchors. Many students have online (线上) classes in some ways (方式) at home.
Some students think having online classes is helpful, because they can keep on(保持) learning at home. With the help of Ding Talk(钉钉), We Chat or 17EdTech, they can have classes, finish homework and even take tests(测试). They can watch the video classes again at anytime and anywhere, too.
But every coin has two sides. Students learn online for a long time, it is bad for their eyes. They study at the desk all day, they're fatter and fatter, and it's bad for them. So students should do more(更多的) things to relax(放松) themselves after classes. They should sing, dance, play sports and so on.
