1 . There are many people in the world now. There will be even _________ people later this century. The earth will he crowded and there will be very little room _________ each person. Maybe there will be only _________ room on the earth in 600 years. That will be a very serious problem, so man is taking some _________ to solve the _________.

The moon is the satellite of the earth. Maybe man will go to live on the moon one day. _________, Americans and Chinese have _________ there. But there is no air, no plants, and no life. So _________ are doing experiments in many ways. They will find _________ to these problem __________ man can live on the moon. I’m sure our dream will come true by the end of this century.

2 . A hundred years ago, the largest city in the world was London, with a population of 6.5 million. Today it is beaten by Tokyo. With barely a quarter the population of London a century ago, the Tokyo metropolitan area has since ______ to 34 million, promoting it to first place in the global city league table. Tokyo’s phenomenal growth is largely due to a single factor: migration from the countryside to the city.

This ______ migration can now be seen in scores of cities around the globe. And it has brought us to a crucial moment in human history. In 1990, most people lived in the countryside, with a little over 10 percent of the world’s population living in ______. From next year, the UN Population Division predicts that for the first time in history, more people will live in cities than in the country, and the biggest growth will be in “mega-cities,” with populations over 10 million.

The ______ of mega-cities - there are now 20 in total - has brought with it huge environmental and social problems. Cities occupy just two percent of the land surface of the Earth but consume three-quarters of the resources that are used up each year. Their residents are making ruinous ______ on soils and water supplies for food and on forests for wood and paper.

______ the world’s population to the countryside isn’t an option. Dividing up the planet into plots of land on which we could all survive self-sufficiently would create its own natural disasters, not to mention being highly unlikely to ever ______. If we are to protect what is left of nature, and meet the demand to improve the quality of living for the world’s developing nations, a new form of city living is the only option. ______, governments, planners, architects, and engineers are beginning to wake up to this idea, and are dreaming up new ways to green the mega-cities. Their approaches ______ two main principles: recycle whatever possible and remove as many cars as possible. So as well as developing energy-efficient buildings, emphasis is being placed on increasing the use of ______ and redesigning how cities are organized to integrate work and living areas into a single neighborhood, rather than ______ cities into residential, commercial, and industrial zones.

Planners and architects now agree that to improve the social and environmental condition of cities the top ______ is to cut car use. They say zero-emission cars running on electricity or burning hydrogen are not ______. What is needed is a wholesale rethink of how new cities are laid out — and how existing ones expand — to ______ the need for cars in the first place. One way of achieving this is to build cities with multiple centers where people live ______ their work in high-rise blocks that are also near public transport hubs. In parts of the world this is already taking place.