The “balance of nature”is not an empty phrase. Nature provides a population to occupy a suitable environment and cuts down surplus population to fit the available food supply. One means of reducing surplus population is predators; others are parasitic diseases. Also, population density produces nervous disorders and even drives animals to mass migrations(移民群),like the lemmings of Norway who plunge（冲入）into the sea.

That predatory population increase to control other animals has long been known. Many years ago, the Hudson’s Bay Company records revealed that the fox population went up and down about a year after rabbit population had gone up and down.

Sometimes a situation occurs in which the predatory population is reduced to a level below which nature can readily replace. On Valcour Island in Lake Champlain, a costly campaign resulted in the elimination（消除）of predatory animals only to have birds and small animals increase for four years afterward. Then, lacking predator control, nature resorted to disease to cut down these populations.

Jamaica had an example of nature’s persistence in providing animals for existing habits. Sugar planters, about 75 years ago, imported mongooses（狐猴）to control rats. The mongooses killed off the rats, kids, puppies, and wildlife. Eventually, food became scarce and the mongoose’s population declines.

1. The fact that the number of predators has much to do with that of other animals 　　  .

A. is not recent knowledge　　　　　　　　　　　　　　    B.has just been learned

C.hasn’t been proved yet　　　　　　　　　　　　　　　　　　　　  D.is not important now

2. When predator control fails, nature brings animal population into balance by       .

A. eliminating the number of predators

B.seeking the help of disease to reduce other animals

C.increasing the number of other animals

D.replacing the number of predators immediately

3. When the mongooses killed off the rats they 　　  .

A. became problems themselves　　　　　　　　　　　　 B.ate the sugar crop

C.attacked humans　　　　　　　　　　　　　　　　　　　　   D.had nothing to eat

4. It is implied in this passage that 　　  .

A. sugar planter imported mongooses to control rats

B.man should never kill animals

C.man has complete control over nature

D.to upset the balance of nature can be troublesome

阅读理解

　　Feeling tired lately? Has the doctor said he cannot find anything wrong with you? Perhaps he sent you to a hospital, but all the advanced equipment there shows that there is nothing wrong. Then consider this, you might be in a state of sub health (亚健康).

　　Sub health, also called the third state or grey state, is explained as a border line state between health and disease. According to an investigation by the National Health Organization, over 45 percent of sub healthy people are middle-aged or elderly. The percentage is seven percent higher among people who work in management positions as well as students around exam time.

　　Symptoms include a lack of energy, depression, slow reactions, insomnia(失眠), agitation(焦虑), and poor memory. Other symptoms include shortness of breath, sweating and aching in the waist and legs.

　　The key to preventing and recovering from sub health, according to some medical experts, is to form good living habits, alternate work with rest, exercise regularly, and take part in open-air activities.

　　As for meals, people are advised to eat less salt and sugar. They should also eat more fresh vegetables, fruits, fish because they are rich in nutritional elements——vitamins and trace elements——that are important to the body.

　　Nutrition experts point out that it is not good to eat too much at one meal because it may cause unhealthy change in the digestive tract(消化道). They also say that a balanced diet is very helpful in avoiding sub health.

(1)According to this passage, which of the following is right?

[　　]

A．When you are in a state of sub health, you should stay home and keep silent.

B．When you are in a state of sub health, you should to go see a doctor and buy some medicine.

C．When you are in a state of sub health, you should have yourself examined in foreign countries.

D．When you are in a state of sub health, you should find out the reasons and relax yourself.

(2)Middle-aged people may feel sub healthy, because ________.

[　　]

A．they have used up their energy

B．they have lost their living hopes

C．they have more pressure in life and work

D．they begin to get older

(3)The answer of preventing you falling into a state of sub health is that you should ________.

[　　]

A．work hard　　　　　B．sleep more

C．keep relaxed　　　　D．take more medicine

(4)The underlined word“alternate”in this passage means ________.

[　　]

A．arrange by turns　　　　B．cause to take place

C．keep up　　　　　　　   D．take up

That predatory population increase to control other animals has long been known. Many years ago, the Hudson’s Bay Company records revealed that the fox population went up and down about a year after rabbit population had gone up and down.

Sometimes a situation occurs in which the predatory population is reduced to a level below which nature can readily replace. On Valcour Island in Lake Champlain, a costly campaign resulted in the elimination（消除）of predatory animals only to have birds and small animals increase for four years afterward. Then, lacking predator control, nature resorted to disease to cut down these populations.

Jamaica had an example of nature’s persistence in providing animals for existing habits. Sugar planters, about 75 years ago, imported mongooses（狐猴）to control rats. The mongooses killed off the rats, kids, puppies, and wildlife. Eventually, food became scarce and the mongoose’s population declines.

1. The fact that the number of predators has much to do with that of other animals 　　  .

A. is not recent knowledge　　　　　　　　　　　　　　    B.has just been learned

C.hasn’t been proved yet　　　　　　　　　　　　　　　　　　　　  D.is not important now

2. When predator control fails, nature brings animal population into balance by       .

A. eliminating the number of predators

B.seeking the help of disease to reduce other animals

C.increasing the number of other animals

D.replacing the number of predators immediately

3. When the mongooses killed off the rats they 　　  .

A. became problems themselves　　　　　　　　　　　　 B.ate the sugar crop

C.attacked humans　　　　　　　　　　　　　　　　　　　　   D.had nothing to eat

4. It is implied in this passage that 　　  .

A. sugar planter imported mongooses to control rats

B.man should never kill animals

C.man has complete control over nature

D.to upset the balance of nature can be troublesome