如图所示，斜面长5m，高1m，工人用沿斜面方向400N的力把重1600N的箱子匀速推到车上，推力对箱子做的功是____J，斜面的机械效率是____．

    How do you get pocket money from your parents? In the western countries, many ____ do housework to get pocket money. They usually start to do this ____ the age of ten.

    Jimmy is seven years old. Now he is ____ the dishes. He can only do this, so he can't get ____ money. But that's all right. He only wants to ____ candies.

    Jenny is twelve years old. She is ____ than Jimmy. She wants to buy many things. They are more expensive than candies.

    ____ she has to work harder! Now she is washing the car. If she ____ free time, she will cut grass, walk the dog or cook dinner.____ housework can help kids learn new things. For example, you can learn how to cook. Of course, your mother will help you at the ____ .

世界上火山、地震最频繁的地区分布在（　　）

下列说法不正确的是（）