B

    We are learning English, but how can we learn English well? A student can know a lot about English, but maybe he can't 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 can learn English only by using it. You must listen to your teacher in class. You must read English every day. You must speak English to your classmates and you must also write something in English sometimes. Then one day, you may find your English very good.

在如图所示的电路中，电阻R₁=12Ω，R₂=8Ω，R₃=4Ω．当电键K断开时，电流表示数为0.25A，当K闭合时电流表示数为0.36A．求：

我国某一盆地，位于地势第二级阶梯，盆地中的沙漠是我国面积最大的沙漠，常常飞沙走石，盆地边缘的山麓地带，高山冰雪融水哺育着一块块绿洲．根据材料并结合图，

" >400毫米年等降水量线和青藏高原边缘线这三条重要的地理界线结合起来，并根据实际情况作一定的调整，就把我国划分为四大地理区域，即北方地区、南方地区、西北地区和青藏地区．该盆地是（ ）

下列是不属于陆地的基本地形的是（  ）