某地夏季高温多雨，冬季温和少雨，最冷月均温在2℃以上，降水量在1100毫米左右，该地

阅读理解。

     A prairie is a type of grassland. Prairies are made up of a complete interdependent ecosystem. This means

that all kinds of plants and animals in a prairie region depend on one another for survival (生存). The members

of a prairie ecosystem include grasses, flowering plants, animals, soil (土壤), sand, and fire.

     You may look at a prairie and think there's nothing there but grass, but that' s not true. Most of the prairie's

living things are below the ground. Underneath the prairie' s surface are roots and bulbs (根茎). The roots of

the prairie flowers and grasses run deep. Some of them are as deep as 3.5 metres below the ground.

     It is impmtant for the roots to run deep because fires are a part of the prairie ecosystem. When a fire bums

through the prairie, plants with shallow (not deep) roots can not survive. Plants that have deep root systems

are able to survive the fires. When fire burns across a prairre, it bums dead plants from the top and returns

those nutrients (养料) to the soil. This adds to the richness of the prairie soil. Prairies have some of the

richest soil in the United States. This cycle of growth and buming has been going on for thousands of years.

Big bluestem is the plant that gives parts of the prairie the name "tallgrass prairie".

     Big bluestem has very deep roots, and its stems (茎) are often 2 metres tall.

     The American bison (野牛) or buffalo, is the country' s largest land animal. Its home is on the prairies. In

1830, there were an estimated 30 million to 60 million bison in the United States. By 1889, Americans had

made the bison population to fewer than l,000 animals. Through great efforts, bison are being reintroduced to

the prairies. They are also kept in zoos. The bison population has grown to several hundred thousand today.

     Humans have put the prairie ecosystem in danger. Through constant farming, building, fire prevention,

and ignorance( not knowing) of how the prairie works, the United States has lost much of its natural prairie.

Through education and other work , we can hope to save some of it.

1. A prairie is a type of  ________.

A. plants

B. animals

C. grassland

D. soil

2. What is the meaning of "interdependent ecosystem" in the first line?

A. All things in a prairie region depend on one another.

B. Animals live on plants in a prairie region.

C. Fire plays an important role in a prairie region.

D. Soil has a close relationship with a prairie region.

3. By 1889, the bison population was ________.

A. about 30 million

B. fewer than a thousand

C. about 60 million

D. several hundred thousand

4. We can leam from the article that ________.

A. fires may destroy a prairie and therefore must be prevented

B. the interdependent ecosystem is both below and above ground

C. the prairie ecosystem is in danger because of farming and building

D. people haven't realized that they are losing their natural prairie

已知A、B、C、D为短周期主族元素，其相对位置关系如图。C与B可形成离子化合物C₃B₂。下列分析正确的是       (　　)。

A．电负性：C>A

B．离子氧化性：C>D

C．氢化物稳定性：A>B

D．原子半径：r(C)>r(B)

使足内翻的肌肉是（）

A.胫骨前肌

B.小腿三头肌

C.腓骨长肌

D.趾长屈肌

E.股四头肌

残损率是指（）

A.残损部分与整件商品的比例

B.残损部分的价值与整件商品价值的比例

C.残损部分的重量与全部商品的比例

D.残损部分与完好部分的比例

常用灭火器主要包括（）。

A、机械（水成膜）泡沫灭火器；

B、二氧化碳灭火器；

C、干粉灭火器；

D、1211灭火器；

E、超细粉体灭火器