A. Keywords. earth,water, land area.

　　Vocabulary. bare, gulf, bay, isthmus, plateau, canyon, plain.

　　You are going to hear a passage about the blue planet--earth.

　　While listening, fill in the blankets with the missing words and get familiar with the difference features of the earth.

　　Seen from space, our earth with water covering 70 percent of its surface, appears as the beautiful blue planet.

　　The bare land areas appear red or brown, dark green shows where there's plant cover, and white means snow.

　　Besides the 7 major land areas, called continents, there are thousands of islands.

　　Some of these are arranged in groups, and some stand alone in the great oceans.

　　Arms of the land which reach out into the water are called peninsulas.

　　Seas, gulfs and bays are arms of the ocean which lie between islands and peninsulas.

　　A narrow piece of land connecting two larger land areas is an isthmus.

　　A narrow stretch of water between two land areas is called a strait or channel.

　　Water is constantly in motion on the earth.

　　Rain water runs off the mountain into valleys, it collects in lakes and rivers, which carry it back to the seas.

　　From the high altitude of mountain passes and plateaus to the canyons and low-lying plains, the features of the land are wonderful to see.

　　B. Keywords. the biggest cities, the top 10, developed countries, developing countries.

　　Vocabulary. complex, enormous, mere, in terms of, quadruple, treble, Sao Paulo,

　　Rio de Janeiro, Calcutta, Bombay, Delhi, Seoul.

　　B1. You are going to hear a conversation between an interviewer and an expert about the biggest cities in the world.

　　While listening, focus on the numbers and complete two chart below.

　　In Britain, we are often told that people are leaving the biggest cities to live in the countryside.

　　But is this the case worldwide?

　　Not at all. If you look at the biggest cities in 1950, 7 out of the top 10 were in the developed countries.

　　But by the year 2000, the developing countries will have 8 out of the top 10.

　　New York, which in 1950 was NO.1 with a population of around 12 million, will only be the sixth largest city in the world, but with extra 2 million.

　　And London? London, which was No.2, won't even be on the top 10.

　　Its population in 1950, by the way, was about 10 million.

　　And why is this happening?

　　Why are people moving to the big cities from the countries and developing countries?

　　The reasons are complex, but many are moving to look for work, and problems this creates are enormous.

　　It's estimated that 26 million people will be living in Mexico City by the year 2000.

　　With Sao Paulo in Brazil not far behind.

　　It's difficult to believe.

　　I know. Rio de Janeiro will have a population of a mere 13 million.

　　Well, just image the kinds of difficulty this is going to cause in terms of health, transport and education.

　　Yes, What about cities of Asia?

　　Will they be experiencing an similar sort of growth?

　　In some cases, yes.

　　Calcutta in India, which was NO.10 in the league in 1950, is expected to be the 4th biggest city in the world with a population of 16 million, quadrupling its size in just 50 years.

　　Bombay in Delhi, too, are expected to be in the top 10.

　　What about Japan?

　　Ah, well, Tokyo was the No.3 in 1950, and that's where it will be at the beginning of next century, although its population will trebled to about 18 million.

　　Looking at the other major cities in Asia, Shanghai and Seoul will be on the top 10 as well.

　　But perhaps surprisingly, not Beijing or Hong Kong.

　　Now if we could turn our attention to home, what about the trend of people moving out of the cities...

　　B2. Now listen to the conversation again.

　　And try to find out the other 7 cities whose population is likely to be in top 10 in 2000.