D. Most people need seven and a half hours of sleep every night.

27. For our bodies to function properly, we should .

A. adjust our activities to the new inventions

B. be able to predict the rhythms of our biological clocks

C. sleep for at least eight hours per night

D. believe that we need less sleep as we age

28.According to the author, many sleeping disorders are caused by .

A. improper sleep patterns

B. chronic fatigue syndrome

C. other diseases

D. pre-bedtime exercises

29. Which of the following measures can help you sleep better?

A. Having late meals.

B. Traveling between time zones.

C. Staying up late.

D. Taking a hot bath.

30. “ Sleep defensively” means that .

A. people should sacrifice other things to getting enough sleep if necessary

B. people should give up going to bed and getting up at the same time every day

C. people should go to a doctor and have their problems diagnosed

D. people should exercise immediately before going to bed every night

Questions 31—35 are based on the following passage:

Passage 3

At Kyoto conference on global warming in December 1997, it is became abundantly clear how complex it has become to work out international agreements relating to the environment because of economic concerns unique to each country. It is no longer enough to try to forbid certain activities or to reduce emissions of certain substances. The global challenges of the interlink between the environment and development increasingly bring us to the core of the economic life of states. During the late 1980s we were able, through international agreements, to make deep cuts in emissions harmful to the ozone layer. These reductions were made possible because substitutions had been found for many of the harmful chemicals and, more important, because the harmful substances could be replaced without negative effects on employment and the economies of states.

Although the threat of global warming has been known to the world for decades and all countries and leaders agree that we need to deal with the problem, we also know that effects of measure, especially harsh measures taken in some countries, would be nullified (抵消) if other countries do not control their emissions. Whereas the UN team on climate change has found that the emissions of carbon dioxide would have to be cut globally by 60% to stabilize the content of CO, in the atmosphere, this path is not feasible for several reasons. Such deep cuts would cause a breakdown of the world economy. Important and populous (人口众多的)low or medium-income countries are not yet willing to undertake legal commitments about their energy uses. In addition, the state of world technology would not yet permit us to make such a big leap.

We must, however, find a solution to the threat of global warming early in the 21st century. Such a commitment would require a degree of shared vision and common responsibilities new to humanity. Success lies in the force of imaginations, in imagining what would happen if we fail to act. Although many living in cold regions would welcome the global-warming effect of a warmer summer, few would cheer the arrival of the subsequent tropical diseases, especially where there had been none.

31. The main purpose of this passage is to .

A. analyze the problem of global warming

B. argue against making deep cuts in emissions

C. convince people that global warming is a real threat

D. criticize some countries for refusing to cut down emissions harmful to the ozone layer

32. The reason why it is difficult to get rid of the threat of global warming is that .

A. the leaders of many countries are not fully aware of the gravity of the problem

B. many people welcome the global-warming effect of a warmer summer

C. not all the countries are willing to make deep cuts in emissions

D. world technology is not able to solve the problem

33. In the passage the author implies that .

A. the world has recently become aware of the threat of global warming