Unit19 Urban and Rural Worlds 城镇与乡村文章学练1Mega-cities In 1950, 1 D. 2 A. 3 C. 4 A. 5 B. 文章学练2A Case Study: Desertification around the Gobi Desert1 D. 2 A. 3 B. 4 A. 5 D. 语法&功能学练.填空补充完成句子。1. There are now 11 cities（which）（house） over 11 million people each.2. The worlds urban population, （which）（is）（increasing）at four times the rate of rural populations, will double in the period 1990 - 2025.3. This growth,（which）（adds）around 60 million people per year to city populat
