计算： $\frac{a}{a-1}$ + $\frac{1}{a-1}$ =____．

黄土高原水土流失严重，主要的人为原因是（    ）

自来水公司调查了若干用户的月用水量x（单位：吨），按月用水量将用户分成A、B、C、D、E五组进行统计，并制作了如图所示的扇形统计图．已知除B组以外，参与调查的用户共64户，则所有参与调查的用户中月用水量在6吨以下的共有（　　）

组别	月用水量x（单位：吨）
A	0≤x＜3
B	3≤x＜6
C	6≤x＜9
D	9≤x＜12
E	x≥12

如图5曲线所示，甲商品的数量（Q）随着价格(P)的变动而变动,这可能说明的关系是

①甲商品的供给量(Q)与自身价格(P)
②甲商品的需求量(Q)与自身价格 (P)
③甲商品需求量(Q)与互补商品价格(P)
④甲商品的需求量(Q)与替代商品价格(P)

读一读，回答下列问题。
    Betty is very happy because she moves to her new home today. Her new home is very big and nice. It has three bedrooms. The big one is for her parents. The small one is for her brother Paul and the middle one is for her. Betty likes pink，so her bedroom is a pink room. The walls are pink. The curtains(窗帘)are pink. The bed and wardrobe(衣柜)are pink, too. Every day, Betty does her homework in her bedroom. Betty's father likes the new home, too. He likes the study because it's quiet. He can read in it. Betty's mum likes the kitchen. It is big and clean. She can cook nice food for the family. Paul likes the new home because the living room is so big and he can play games with his friends there.