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rough each draft and provided me with inspiring advice. without her patient instruction, insightful criticism and expert guidance, the pletion of this thesis would not have been 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 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 plaint.