A They become less stable as they mature.

B They support many species when they reach climax.

C They are found in temperate zones.

D They have reduced diversity during mid-successional stage.

9 In paragraph 5,why does the author provide the information that“a A fifteen-speed racing bicycle is more likely to break down than a child’s tricycle”?

A To illustrate a general principle about the stability of systems by using an every-day example.

B To demonstrate that an understanding of stability in ecosystem can be applied to help understand stability in other situations.

C To make a comparison that supports the claim that,in general,stability increases with diversity.

D To provide an example that contradicts mathematical models of ecosystems.

11 which of the sentences below best expresses the essential information in the highlighted sentence in the passage?Incorrect choices change the meaning in important ways or leave out essential information.

A Ecologists now thinks that the stability of an environment is a result of diversity rather than patchiness.

B Patchy environments that vary from place to place do not often have high species diversity.

C Uniform environments can’t be climax communities because they do not support as many types of organisms as patchy environments.

D A patchy environment is thought to increase stability because it is able to support a wide variety of organisms.

Writing（30分）

Some people think that strict punishments for driving offences are the key to reducing traffic accidents.Others,however,believe that other measures would be more effective in improving road safety.

Discuss both these views and give your own opinion.