Acknowledgments

Upon the completion of this research，I would like to extend my heartfelt gratitude and great appreciation to all those who have contributed to it either directly or indirectly.

First and foremost，I am deeply indebted to Professor He Zhao xiong，my supervisor，for his insightful advice，patient guidance and constant encouragement in the research.From the very beginning till the end，he had never ceased to pay attention to it，though he was very busy with coursebook revision，teacher training，TEM scoring，and other social activities.Any deviation or deficiency in the choice of diction，expression of meaning，and discourse organization never succeed in escaping his critical eyes.I have been deeply touched by his sedulous and meticulous scholarship and learned a lot from his most excellent humane qualities both as a researcher and as a professor.Without his effective guidance，invaluable suggestions，and encouragement，this program would not have been possible.

Secondly，I would like to express my sincere thanks to all the other faculty members of SISU who have taught me and enlightened me in my studies，including Prof.Dai Weidong，Prof.Mei Deming，Prof.Zou Shen，Prof.Yu Jianhua，Prof.Xu Yulong，Prof.Li Weiping，and Prof.Shu Dingfang.My thanks also go to Prof.Hong Gang，and Prof.Hou Guojin；inspiring discussions with them through e-mail were also significant for the final wording of the research.

Special thanks also go to Prof.Li Yanqing，my former party secretary，bosom friend，and Big Sister，for persistently reminding me of my academic pursuit while I was indulged in daily teaching and administrative affairs.Prof.Wei Yaozhang made critical comments on my research design and encouraged me，when I was depressed in the course of writing.Prof.Ma Shengcang frequently phoned me to enquire about the progress of my project.Thank them all！

Last but not the least，I should say thank you to my family，especially my wife，who supported me in my pursuit of my academic dream without any complaints，taking over all of the load of the housework and caring for our daughter and son during my research.I am also indebted to my pupils and Ningxia Provincial Department of Education，whose positive attitude and kind cooperation and whose financial support in my survey allowed the research to be completed as scheduled.As for the shortcomings that remain，the author alone is held responsible.