登楼

杜甫

花近高楼伤客心，万方多难此登临。

锦江春色来天地，玉垒^①浮云变古今。

北极朝廷终不改，西山寇盗^②莫相侵。

可怜后主还祠庙，日暮聊为梁甫吟^③。

【注】①玉垒：山名。②西山寇盗：指吐蕃。③梁甫吟：《三国志》说诸葛亮躬耕陇亩，好为《梁甫吟》。

C

    Many people today like exercise. Some like to run, and some like to walk. Others dance or play balls. They do different kinds of exercise. Why do people like exercising? It's good for their health. And exercise helps make them tired, so they sleep better at night.

    You may like to run. If you do, take care of your feet. Make sure you have the right shoes. Some people like to run on roads, but they must watch out for cars.

    Walking is a good exercise. You may take a long walk in the park. It's more fun if you don't go alone. Go with a friend. The two of you may have a great time.

    Some people like to swim. But others don't like to go into the water. If you like this kind of exercise, make sure that someone is watching you. You must always take care when you are in the water. Jumping a rope (跳绳) or riding a bike is also good exercise. There are many other exercises. Find out what you like. You may need help at first. Some people often do exercise, and they can help you. Do exercise every day, and you will know what it makes you feel.

    二世元年七月，发闾左谪戍渔阳九百人，屯大泽乡。陈胜、吴广皆次当行，为屯长。会天大雨，道不通，度已失期。失期，法皆斩。陈胜、吴广乃谋曰：“今亡亦死，举大计亦死，等死，死国可乎？”陈胜曰：“天下苦秦久矣。吾闻二世少子也，不当立，当立者乃公子扶苏。扶苏以数谏故，上使外将兵。今或闻无罪，二世杀之。百姓多闻其贤，未知其死也。项燕为楚将，数有功，爱士卒，楚人怜之。或以为死，或以为亡。今诚以吾众诈自称公子扶苏、项燕，为天下唱，宜多应者。”吴广以为然。

关于x，y方程组$\left\{\begin{array}{c}{x}^2+2y^2=6\\ mx+y=3\end{array}\right.$有一组实数解，那么m的取值范围是（　　）