阅读理解

    Tom,Bill and Dave lost their backpacks．They are at the lost and found office．The backpacks are the same(相同的),but the things in them are different．Can you help them find the right(正确的)backpack?

    Tom：I have a  maths book and a pencil case in my backpack．There are three pencils,a pen and an eraser in the pencil case．

    Bill：I have a Chinese dictionary,a maths book and two notebooks in my backpack．

    Dave：There are two CDs,three picture books in my backpack．My English book is also in it．

①货币流通速度加快 
②货币的实际供应量增加

③货币周转次数减少 
④流通中所需的货币量减少

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：

下图为亚洲某国年降水量分布图。下列结论的依据，所用图示信息正确的是（    ）

有理数a、b、c满足a+b+c=0，abc=-9，则a、b、c中负数的个数是（　　）