We are learning English, but how can we learn English well? A student can know a lot about English, but maybe he can not speak English.
If you want to know how to swim, you must get into the river. And if you want to be a football player, you must play football. So , you see, you can learn English only by using it. You listen to your teacher carefully in class. You must read your lessons every day. You must speak English to your English teacher and classmates and also you must write in English. Then one day, you may find your English very good.

对正处在生长发育时期的青少年来说，一日三餐都很重要．根据合理营养的要求，在每日摄取的总能量中，哪餐摄入的能量应最多（　　）

2xy²+x²y²﹣7x³y+7按x的降幂排列：____．

已知铜绿Cu₂（OH）₂CO₃在加热时分解生成A,B,C三种常见的氧化物，下面是有关物质之间的转化关系图示（部分生成物未标出）

在学习依法治国的内容时，几个同学就有关“依法治国”的问题展开了热烈的讨论。下列观点错误的是（    ）