I would like to express my gratitude to all those who have helped me during the writing of this thesis. I gratefully acknowledge the help of my supervisor Professor Zhu Jimei. I do appreciate her patience, encouragement, and professional instructions during my thesis writing. Also, I would like to thank Miss Wen Pingzhen and Miss Li Wenying, who kindly gave me a hand when I was making the questionnaire among the college English learners.
Last but not the least, my gratitude also extends to my family who have been assisting, supporting and caring for me all of my life.
I am greatly indebted to my supervisor, Professor Wang Shuting, for his valuable instructions and suggestions on my thesis as well as his careful reading of the manuscript.
I feel grateful to all the teachers in the College of Foreign Languages of China University of Petroleum who once offered me valuable courses and advice during my study. My sincere thanks are also given to Pro. Dai Ruiliang and Pro. Sun Chengrong. from whose lectures I benefited greatly.
Last but not least, I owe much to my friends and classmates for their valuable suggestions and critiques which are of help and importance in making the thesis a reality.
I would like to express my gratitude to all those who helped me during the writing of this thesis. I gratefully acknowledge the help of my supervisor, Ms. Sun Yanlan, who has offered me valuable suggestions in the academic studies. In the preparation of the thesis， she has spent much time reading through each draft and provided me with inspiring advice. Without her patient instruction, insightful criticism and expert guidance, the completion of this thesis would not have been possible.
I also owe a special debt of gratitude to all the professors in Foreign Languages Institute, from whose devoted teaching and enlightening lectures I have benefited a lot and academically prepared for the thesis.
I should finally like to express my gratitude to my beloved parents who have always been helping me out of difficulties and supporting without a word of complaint.