AcknowledgementsI have spent several months going through this long journey of writing this thesis, in which I encountered lots of dilemmas and bottlenecks
Fortunately, I overcome all the difficulties that once disappointed me
However, I have benefited a lot from it, and I have gained more knowledge and enlightenment from it than I ever expected
Firstly, I would like to show my gratitude to our university for providing me with such a valuable opportunity of writing this thesis to conclude my precious four years’ undergraduate education
And my most sincere appreciation belongs to my respectable supervisor, Mrs
Wang Yang, an knowledgeable and amiable teacher, who has given me many needed helps and considerable suggestions patiently and painstakingly and has fulfilled the task of reading,