由一个主题句(topic sentence)和几个支持句(supporting sentence)组成。中心段一般有两种
For the time being, the most urgent task is to briny the big rivers，such as Yangtze River，XianJiang River. Gan,jiang River, etc, under control . For this purpose，We must dredge these rivers .Silt must be got rid of from the rivers，beds of rivers be broadened and banks be heightened.These measures will relieve to some degree the harm of the floods .But in the long run，if we want to harness floods thoroughly, some other measure should be taken . As is known，the profound cause of floods is the destruction of vegetation in the areas of the rivers .So we must take action to stop the acts of environmental destruction .Areas of vegetation should be expanded in these areas .Only by the temporary and the radical measures can we hope to bring the rivers under control.
It is well known that most of the poor people live in the old revolutionary base areas or the areas inhabited by minority nationalities .A common factor that hinders the development of these areas is backward transportation and communication .Therefore, the government should help these areas develop the facilities of transportation and communication so that they can be connected with the outside world in formation as well as in commercial trade .This is the first step in eliminating poverty.