我国政府允许养老保险基金保值增值的途径是( ) A．银行存款 B．国债 C．风险小

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

（理）有3张都标着字母R，5张分别标着数字1，2，3，4，5的卡片，若任取其中4张卡片组成牌号，则可以组成的不同牌号的总数等于 （用数字作答）

（文）在5张分别标着数字1，2，3，4，5的卡片中，任取其中3张卡片，和3张都标着字母R的卡片一同组成牌号，则可以组成的不同牌号的总数等于（用数字作答）.

甲公司将1台挖掘机出租给乙公司，为担保乙公司依约支付租金，丙公司担任保证人，丁公司以机器设备设置抵押。乙公司欠付10万元租金时，经甲公司、丙公司和丁公司口头同意，将6万元租金债务转让给戊公司。之后，乙公司为现金周转将挖掘机分别以45万元和50万元的价格先后出卖给丙公司和丁公司，丙公司和丁公司均已付款，但乙公司没有依约交付挖掘机。因乙公司一直未向甲公司支付租金，甲公司便将挖掘机以48万元的价格出卖给王某，约定由乙公司直接将挖掘机交付给王某，王某首期付款20万元，尾款28万元待收到挖掘机后支付。此事，甲公司通知了乙公司。王某未及取得挖掘机便死亡。王某临终立遗嘱，其遗产由其子大王和小王继承，遗嘱还指定小王为遗嘱执行人。因大王一直在外地工作，同意王某遗产由小王保管，没有进行遗产分割。在此期间，小王将挖掘机出卖给方某，没有征得大王的同意。

在乙公司将6万元租金债务转让给戊公司之后，关于丙公司和丁公司的担保责任，下列表述正确的是：（）

A．丙公司仅需对乙公司剩余租金债务承担担保责任

B．丁公司仅需对乙公司剩余租金债务承担担保责任

C．丙公司仍应承担全部担保责任

D．丁公司仍应承担全部担保责任

因总监理工程师在项目监理中决策不当，给发包人造成损失时，发包人应当要求( )赔偿。

A．监理单位
B．总监理工程师
C．监理单位的法定代表人
D．具体的监理人员

高频保护投入跳闸前，必须交换线路两侧（），确认正常后，方可将线路高频保护两侧同时投入跳闸。