special thanks should also go to all the excellent professors who have taught mein this university over the past two years, for leading me into the field of researchwork, and giving me tremendous inspiration, courage and confidence during my studyhere. their insightful lectures have made my study delightful and enjoyable.

　　finally, i am also deeply indebted to all my family members and friends for theirencouragement which inspires me every time when i have no motivation to continue.

　　i must mention all my roommates, who give me a comfortable atmosphere to studyand do me a lot of favor when i need help.

　　致谢五:

　　this thesis would not have been possible without constructive advice and helpfrom many persons.

　　first and foremost, i wish to express my sincere gratitude to my supervisor inchina foreign affairs university, professor ran jijun, for his great advice andguidance on the content and format of this thesis, which is critical for revision.

　　without his academic guidance, i could not have accomplished this thesis.

　　i would like to express my appreciation to all my teachers in the englishdepartment of china foreign affairs university, especially to professor he yinghong,professor guo liqiu, professor sun jisheng, professor zhang lei, professor songaiqun, professor wei lamei and professor he qun for everything i have learned fromthem during the two years at this university.

　　also, the emotional support from my parents and my husband is no less importantthan the academic assistance.

　　in the end, i would like to express my thanks to my colleagues who helped collectuseful reference books and materials for me.

　　致谢六:

　　my sincere gratitude firstly goes to my supervisor associate professor xu whohas been providing me enlightening suggestions, careful proofreading and constantencouragement during the whole process of my thesis writing. without his infinitesupport and illuminating guidance, i would never have been able to finish this thesis.

　　moreover, his serious scholarship and academic practices, his conscientious andacademic attitude towards teaching and above all, his agreeable personality, haveinfluenced me immensely during the past three years, which also will be a life-longwealth for me.

　　appreciation also goes to other professors and teachers in the school of foreignstudies, cumt, who have helped me in my postgraduate studies and enlightened meduring the past three years.

　　besides, i feel deeply indebted to my parents and friends, who have helped mesubstantially through the tough process of thesis writing. my special thanks go to mybest friends whose great help and support have accompanied me all the way in thelong and rewarding experience of writing this thesis.