住宅(小区)通信网络系统包括()。A.电话网 B.有线电视网 C.宽带接入网 D.家

某种药品经过两次降价，每盒药品的售价降低到原来的36%，若平均每次降价的百分比为x，则可列方程为（　　）

A．（1-x）²=36%

B．（1-x）²=1-36%

C．2x=1-36%

D．2x=36%

东非大裂谷宽约几十至200公里，深达1000至2000米，是世界上最大的裂谷带。读下图完成下列各题。

小题1:对图中所呈现岩石的说法，正确的是

A．经历了地壳的抬升运动

B．受到了明显的水平挤压作用

C．岩石中不会有化石

D．岩石是由岩浆冷凝形成的小题2:下列四幅图中，能反映东非大裂谷地质构造的是

设向量组α₁=(1，0，1)^T，α₂=(0，1，1)^T，α₃=(1，3，5)^T不能由向量组β₁=(1，1，1)^T，β₂=(1，2，3)^T，β₃=(3，4，a)^T线性表出．①求a的值；②将β₁，β₂，β₃用α₁，α₂，α₃线性表出．

Today anyone will accept money in exchange for goods and services. People use money to buy food, furniture, books, bicycles and hundreds of other things we need or want. When they work, they usually get paid in money.

Lots of the money today is made of paper. But people used to use all kinds of things as money. One of the first kinds of money was shells. Shells were not the only things used as money.

In China, cloth and knives were used. In the Philippine Islands, rice was used as money for  a long time. Some Africans once used elephant tusks, monkey tails, and salt as money.

The first metal coins were made in China. They were round and had a square hole in the center. Different countries have used different metals and designs for their money. Later, countries began to make coins of gold and silver.

But even gold and silver were inconvenient if you had to buy something expensive. Again the Chinese thought of a way to improve money. They began to use paper money. The first paper money looked more like a note from one person to another than the paper money used today.

Money has had an interesting history, from the days of shell money until today.

小题1: In the Philippines Islands ______ was once used as money.

A．rice

B．knife

C．cloth

D．wheat小题2:What was first used as money? ______.

A．Elephants tusks

B．Cloth

C．Salt

D．Shells小题3:The first metal coins looked like ______.

A．square-shaped with some designs on them

B．square-shaped with a round hole in the center

C．round-shaped with a square hole in the middle

D．round-shaped with a round hole in the middle小题4:The first paper money ______.

A．was passed from west Asia to China

B．looked like a note used today

C．was first used in Europe

D．looked like a piece of fur小题5:We can infer from the passage that ______.

A．paper money isn’t difficult to make

B．money must be suited to carry

C．people need money to exchange goods with each other

D．people prefer metal coins to paper notes

蝴蝶图