The change in…mainly results from…
　　The increase in…is due to the fact that…
　　Many people would claim that…
　　One of the reasons given for is that…
　　There are a variety of reasons for this dramatic growth in… First… Second… Finally…
　　Why are (is/do/did)…? For one thing… For another…
　　History is filled with the examples of…
　　As is shown in the table released by the government, it can be learned that…
　　There is (no) good evidence to…
　　We must admit the undeniable fact that…
　　No one can deny the fact that…
　　Experience (Evidence) suggests that…
　　The same is true of…
　　結(jié)尾段的常用核心句型
　　It is high time that we placed great emphasis on the improvement of…
　　It is high time that we put an end to the unhealthy situation (tendency/phenomenon) of…
　　There is no easy solution to the problem of…, but… might be useful.
　　Unless there is a common realization of…, it is very likely that…
　　It is essential that effective measures should be taken to prevent the situation.
　　It is suggested that great efforts should be made to control the growth of…
　　It is hoped that great efforts should be focused on finding (developing/improving)…
　　Anyway, more publicity should be given to the potential effects of…
　　To control the tendency is not an easy job, and it involves a different state of attitude towards…
　　To put all into a nutshell, I…