____in a white uniform,he looks more like a cook than a doctor.

A.Dressed 　　　 B.To dress 　　　　 C.Dressing 　　　　 D.Having dressed

Plants are chemical factories. Many of the chemicals that they produce are useful to humans. Besides food, plants provide material for paper, buildings, medicines and many others. Scientists study the chemicals to treat certain types of cancer.

On the other hand, the fast growth of the human population is changing the earth quickly. Only by understanding how human activities affect our environment can we predict global climate changes. Scientific studies of these changes and their effect on natural ecosystems and crop production are of great importance to the future of our society.

Other environmental issues, such as pollution, also interest scientists. Many plant species are especially sensitive to certain pollutants. Scientists study the effects of different types of pollution on plants. They use their results to advise lawmakers to make laws for environmental protection and to save priceless natural areas.

By using plant tissue culture（植物細胞培養(yǎng)），scientists can grow plants from single cells. This has exciting possibilities in biotechnology, forestry and so on. For example, the American chestnut was once a widespread tree in the Eastern forests. Today it has nearly disappeared because of a disease-producing fungus that causes chestnut to die. The American chestnut recently has been grown in plant tissue culture.

The earth’s biological diversity or the kinds of living things are decreasing. As humans change the environment for their own purposes, plants and animals living in these areas become increasingly endangered．Scientists work to identify and understand new plant species, especially in such biologically rich areas as rain forests. Perhaps a plant undiscovered now will become an important food crop. There are probably many undiscovered plants that produce useful drugs to cure or treat human disease. Biological diversity also provides an important source of new genes to improve the plants we now use. As techniques of genetic engineering improve, so will our ability to improve our plants.

1．Which of the following is not true according to this passage?

A．All the chemicals we need are produced by plants.

B．If we can understand how human activities affect our environment, we can predict global climate changes.

C．Science plays an important role in improving the plants.

D．Scientists use their scientific study results to make laws for environmental protection and to save priceless natural areas.

2．We can know from the Paragraph2 and Paragraph3 that_______.

A．it is global climate changes that endanger plant

B．human activities influence plants greatly

C．pollution does little harm to many plants

D．scientific studies on plant species are important to stop pollution

3．The underlined sentence means___________.

A．plants can produce many chemicals needed in chemical factory

B．plants can be made into many products in factories

C．scientists can use plants to study many chemicals

D．scientists can offer people many necessary materials

4．The importance of biological diversity lies in that_____________________.

A．we can have new species to take the place of the endangered

B．it can populate the earth with as many plants as possible

C．it has many possible values to human being

D．people may use it to cure or treat human disease

5．The best title for the passage might be ____________.

A．Finding New Plant Species

B．Botany and Society

C．The Chemical Factories

D．New Genes to Improve the Plants

Through thorough investigation, Dr. John Snow was finally able to prove that the outbreak of Cholera _____ people’s drinking of polluted water.

　 A. was close linked with B. closely linked to C. was close connected with D. was closely linked with

I never dreamed of　　　　　　　　　　　 (有這么好的酒) in this town.

We should talk about the things________the children’s understanding in a simple way.

A．over B．beyond　　 C．a(chǎn)bove D．under

The teacher usually grades the students on _______ they have behaved.

A. that　　 B. what　　 C. which　　 D. how

The____________ house smells as if it hasn't been lived in for years.

A. little white wooden　　 B. little wooden white

C. white wooden little　　 D. wooden white little

We have got no _______（意向）of staying indoors on a nice sunny day like this. What about you?

The man will have to wait all day ______ the doctor works faster.

A. if　　　　　　 B. unless　　　　　 C. where　　　　　　　 D. that