精选优质文档-倾情为你奉上AcknowledgementsI am very grateful to my supervisor Ms.Zhang who gave me encouragement, careful guidance and helpful advice to me throughout the writing of this thesis. It is she that not only gave me many valuable advices but also let me know how to write this topic. Whats more, I should express my gratitude to Ms. Zhang again for her insightful advice on my choice of the topic and valuable comments on my thesis. I am also indebted to my other teachers who had given me t
