阅读下列材料，结合所学内容回答问题

    雄赳赳，气昂昂，跨过鸭绿江！保和平，卫祖国，就是保家乡！中国好儿女，齐心团结紧，抗美援朝，打败美国野心狼！

     Bruno was a boy of eight. His father worked in a cinema and his mother worked in a shop. He lived not far from his school. He always walked there and walked home. On his way to school, he had to pass a playground. It was very wet after it rained. One day,when he got home,his clothes were all wet. His mother became angry and said,” don't play in the water on your way home from school!”
    On the next day Bruno came back wet and dirty（脏的）clothes. His mother became even angrier.” I'll tell your father you come back wet again.” said his mother,” He'll punish you,you know.”
    The third day the little boy was dry when he came home.“you're a good boy today,” his mother said happily,”you didn't play in the water.”
   “No,” the boy said unhappily.” There were too many older boys in the water when I got there this afternoon. There wasn't any room（空地方） for me at all.”

社会经济的发展推动着城市化进程，“世界城市化水平趋势图”表明21世纪（    ）