56. You have made an appointment with Prof. Wang, but failed to keep it. Write a letter to your teacher. Your letter should include:

　　1 ) apologize for your failure to keep the appointment

　　2) explain your reason to your teacher

　　3) express your wish to make another appointment

　　You should write about 100 words. Do not sign your name at the end of your letter. Use "Li Ming" instead. You do not need to write the address.