Suburbia （郊区） As the cities became more crowded and as the means of transportation improved, middle-class residents （居民）of the city began to move out. In the suburbs they could find ____41___ (safe), more attractive places to live, with open space and greenery around them; yet they could travel daily to the city for their work or business. They could also attend ____42___ (culture) events or gatherings in the city. Soon the remote farmlands and ___43___ (wood) around cities turned into residential neighborhoods. Schools were ___44___ (establish), and various types of business sprang up to serve the needs to the suburban population. During the past two or three decades, many shopping malls have been ____45____ (build) in the suburbs. These large centers, located on main traffic road, include mainly supermarkets, clothing stores, restaurants, and sometimes movie theatres. Their great ___46_____ (attract) for people living in the suburbs is that they are not only near the city, but also they can have enough parking space. The chief problems of city shopping ____47_____ (be) thus avoided. Politically, the suburbs have been independent units, with their own local government ____48___ (run) their schools, their police and fire-fighting organizations and other important services. This ____49____ (arrange) has both advantages and disadvantages. Because the politic units are small, services have ___50____ (usual) been excellent. But from the view of the city residents, it’s fair, since it allows the people of the suburbs to use the city’s facilities and services without carrying a share of the city’s tax burden.
7、____.
【正确答案】：are
【题目解析】：根据句子分析成分，主语是problems，空格是谓语，后面是avoided，表达是问题被避免，用被动语态，be改成are，跟后面的avoided，构成一般现在时的被动语态。
