应该采取适当的措施限制外国旅游者的数量，努力保护当地环境和历史不受国际旅游业的不利影响。
an increasing number of experts believe that migrants will exert positive effects on construction of city .however ，this opinion is now being questioned by more and more city residents ，who complain that the migrants have brought many serious problems like crime and prostitution.
越来越多的专家相信移民对城市的建设起到积极作用。然而，越来越多的城市居民却怀疑这种说法，他们抱怨民工给城市带来了许多严重的问题，象犯罪和卖淫。
many city residents complain that it is so few buses in their city that they have to spend much more time waiting for a bus ，which is usually crowded with a large number of passengers.
许多市民抱怨城市的公交车太少，以至于他们要花很长时间等一辆公交车，而车上可能已满载乘客。
there is no denying the fact that air pollution is an extremely serious problem ：the city authorities should take strong measures to deal with it.
无可否认，空气污染是一个极其严重的问题：城市当局应该采取有力措施来解决它。
an investigation shows that female workers tend to have a favorable attitude toward retirement.
一项调查显示妇女欢迎退休。