题目内容：

The koala, one of Australia’s most treasured creatures, is in trouble.

    Affected by habitat (栖居地) loss and climate change, like many other uniquely Australian animals, koalas are being squeezed into smaller regions. But at present, it is a deadly disease, a somewhat silent killer that causes a further decline in the koala population, that is worrying many scientists about the fate of the koala.

    The killer is Chlamydia, which has caused symptoms in up to 50 percent of the wild koalas, with probably even more infected (感染) but not showing symptoms. It has been particularly severe in Queensland, where nearly all koalas are infected. The disease causes many symptoms including eye infections, which can lead to blindness, making it difficult for them to find their primary food.

    Treating Chlamydia in wild koalas is a challenge. There is no treatment available for it. Only a small percentage of the animals can be treated successfully and returned to the wild. Besides, there is no national plan in Australia to save the koala; it is up to each region to make management plans for its koala population.

    The good news is that researchers are working to test a vaccine (疫苗) that would help prevent further spread. If all goes well, plans can be carried out to distribute the vaccine more widely. But it’s impossible to vaccinate (给注射疫苗)  all wild koalas.

Another possibility would be to make vaccine distribution a routine part of treatment for the thousands of koalas brought into care centers every year after they are injured by cars or dogs.

While it is a combination of problems that are affecting the wild koala population, many experts believe this vaccine would be an important step in helping koalas survive longer. It may be enough time to give researchers a chance to solve some of the other problems facing Austalia’s koalas.

1.Which isn’t considered the main cause of koala’s population decline?

A. A deadly disease.       

B. Injuries from cars and dogs.

C. Climate change.         

D. Habitat loss.

2.The third paragraph mainly tells us          .

    A. the serious result Chlamydia has caused to the koala

    B. Chlamydia affected the koala only in particular regions

    C. the most serious symptom of Chlamydia is eye infections

    D. Chlamydia can seriously affect koala’s primary food

3.We can learn from the text that the vaccine       .

    A. would cure the killer Chlamydia quite effectively

    B. would only be distributed in koala care centers

    C. has already been put into practical use in Australia

    D. cannot be distributed to all the infected koalas

4.It can be inferred from the text that         .

    A. a national plan for saving koalas will be made soon in Australia

    B. koala population is declining only in a few regions

    C. researchers need enough time to solve the koala problems

D. experts have lost the best chance to save the infected koalas