专八小讲座 7 I. The lecture is about the (1)__________ of the world population. II. Two major reasons explain why people are moving to cities. A. The first reason is (2)__________ . People are moving to the cities because that's where they can find jobs and earn money. B. The second reason has to do with quality of life issues: (3)__________ . An interesting consequence of that is that the average age of people in the countryside is increasing, while that of the cities is falling. III. Three key changes can be identified in our cities. A. First, cities are getting bigger. B. Besides, cities are also changing shape. They're getting (4)__________ , because land is getting more and more expensive. Cities are also changing shape in other ways. The (5)__________ Model and the (6)__________ Nuclei Model are probably more typical of the cities we know today. They show the urban (7)__________ that's taking place in modern cities. C. The third change is that our cities are breaking up into smaller communities, often by (8)__________ group or (9)__________ level. IV. The biggest challenge facing us now is to improve the (10)__________ in cities.