It is not rare in __________ that people in __________ fifties are going to university for further education.  

A．90s; the

B．the 90s; 不填

C．90s; their

D．the 90s; their

当前我国某些地区城乡经济出现盲目发展、重复建设、生态环境遭受破坏等现象，其主要根源是( )。

A．当地的资源与环境容量有限

B．城市化快速发展阶段出现的矛盾

C．缺乏区域城乡协调发展机制

D．城市规划的编制滞后于区域经济发展