Today’s lecture is about the mass (1) of the world’s population. There are two major (2) why people are moving to cities. The first reason is (3) . People are moving to the cities because that’s where they can find (4) and earn money. The second reason for the move to cities has to do with (5) of life issues: comfort and (6) . Cities often offer better (7) . And then for many, city life is just more (8) . An interesting consequence of urbanization is that the average (9) of people in the countryside is increasing, while that of the cities is (10) .
Three key (11) can be identified in our cities. First of all, they’re getting bigger. Most cities are bigger now than ever before. Cities are also changing shape. They’re getting (12) , because land is getting more and more expensive. (13) have become a symbol of modern cities.
Cities are also changing shape in other ways. The (14) Model and the (15) Nuclei Model are probably more typical of the cities we know today. They show the urban (16) that’s occurring in contemporary cities.
The third change is that our cities are breaking up into (17) communities, often by (18) group or (19) level. This often means that people stay within their community and do not come into contact with others from different (20) .

根据下图提供的信息，回答96～100题。

全国2007年认定登记的技术合同共计220868项，同比增长7%，总成交金额2226亿元，同比增长22.44%；平均每项技术合同成交金额突破百万元大关，达到100.78万元。

2007年全国共签订技术开发合同73320项，成交金额876亿元，分别比上年增长13.5%和22.2%；共签订技术转让合同11474项，成交金额420亿元，成交金额同比增长30.8%；技术服务和技术咨询合同成交金额分别为840亿元和90亿元，分别比上年增长了20.9%和5.9%。

2007年，在全国认定登记的技术合同中。涉及技术秘密，计算机软件，专利，集成电路，生物医院，动植物新品种等各类知识产权的技术合同共计109740项，成交金额1477亿元，较上年增长23.5%，其中，技术秘密和计算机软件著作权的技术交易成交额居第一，第二，技术秘密合同成交76261项，成交金额1008亿元，较上年增长29.2%。计算机软件著作权合同成交27617项，成交金额255亿元，较上年增长了15.4%。

下列关于2006年技术开发、技术转让、技术咨询和技术服务等四类合同占全国成交会额比重的图形，描述正确的是（）。

A．A

B．B

C．C

D．D