Scientists are closely concerned with the structure of buildings and with the quality of building materials． The World health Organization （WHO) observes that the introduction of air conditioning and energy conservation （保护) measures have been accompanied by growing problems of indoor air quality． Some pollutants arise from insulation （隔音) products, some from moving cars, and others from modern housing materials． As many Europeans spend up to 90% of their lives in buildings, the health effects of the indoor climate are very important．
　　Some construction materials, including fiberboard, insulation foams and certain glues for man-made wood floor boards, for example, give out organic products such as formaldehyde （甲醛)． Heat and humidity increase the release of formaldehyde and the gas seriously harms the eyes． Paint, lacquer, etc． can also release dangerous gas into indoor air．
　　Construction materials can cause serious damage, especially when they contain asbestos（石棉）． Asbestos is naturally present in rock formations worldwide． It belongs to a family of mineral substances made up of solid, non-combustible（非易燃品） fiber． These properties make asbestos a highly sought-after construction material． As early as 1931, however, public health officers in the United Kingdom revealed the connection between breathing in asbestos dust and such diseases as lung cancer．
　　The land on which a building is sited may also contribute to pollution． Some kinds of granite or similar rocks contain traces of radium． As it breaks down, this naturally radioactive element produces some kind of radioactive gas that goes through tiny cracks in walls, floors and building materials, and makes its way into the building and the rooms． The better the homes are insulated, the more is the dangerous gas in indoor air． The main effect of this dangerous gas on health is to increase the risk of lung cancer．
【小题1】What is the main idea of the passage?

It is you, rather than he, that　　　for the accident．

       A．is to blame　　　　       B．are to blame      C．is blame　　　　    D．are blame

Have you ever wondered why birds sing? Maybe you thought that they were just happy. After all, you probably sing when you are happy. Some scientists believe that birds do sing some of the time just because they are happy. However, they sing most of the time for a very different reason. Their singing is actually a warning to other birds to stay out of their territory.
　Do you know what a “territory” is? A territory is an area that an animal, usually the male, claims (声称) as its own. Only he and his family are welcome there. No other families of the same species are welcome. Your house is your territory where only your family and friends are welcome. If a stranger should enter your territory and threaten you, you might shout. Probably this would be enough to frighten him away. If so, you have actually frightened the stranger away without having to fight him. A bird does the same thing. But he expects an outsider almost any time, especially at nesting (筑巢) season. So he is screaming all the time, whether he can see an outsider or not. This screaming is what we call a bird’s song, and it is usually enough to keep an outsider away.
【小题1】Some scientists believe that most of the time bird’s singing is actually ________.
A.an expression of happiness      B. a way of warning
B.an expression of anger          D. a way of greeting
【小题2】What is a bird’s “territory”?

Have you ever wondered why birds sing? Maybe you thought that they were just happy. After all, you probably sing when you are happy. Some scientists believe that birds do sing some of the time just because they are happy. However, they sing most of the time for a very different reason. Their singing is actually a warning to other birds to stay out of their territory.

　Do you know what a “territory” is? A territory is an area that an animal, usually the male, claims (声称) as its own. Only he and his family are welcome there. No other families of the same species are welcome. Your house is your territory where only your family and friends are welcome. If a stranger should enter your territory and threaten you, you might shout. Probably this would be enough to frighten him away. If so, you have actually frightened the stranger away without having to fight him. A bird does the same thing. But he expects an outsider almost any time, especially at nesting (筑巢) season. So he is screaming all the time, whether he can see an outsider or not. This screaming is what we call a bird’s song, and it is usually enough to keep an outsider away.

1.Some scientists believe that most of the time bird’s singing is actually ________.

A.an expression of happiness      B. a way of warning

B.an expression of anger          D. a way of greeting

2.What is a bird’s “territory”?

A．A place where families of other species are not accepted.

B．A place where a bird may shout at the top of its voice.

C．An area for which birds fight against each other.

D．An area which a bird considers to be its own.

3.Why do birds keep on singing at nesting season?

A．Because they want to invite more friends.

B．Because their singing helps frighten outsiders away.

C．Because they want to find outsiders around.

D．Because their singing helps get rid of their fears.

4.How does the writer explain birds’ singing?

A．By comparing birds with human beings.       B．By reporting experiment results.

C．By describing birds’ daily life.             D．By telling a bird’s story.

5.What does the underline word “screaming” in paragraph 4 mean?

A．哭喊声           B．令人惊愕的        C．尖叫声           D．尖叫的