You have just come back from the U.S. as a member of a Sino-American cultural exchange program. Write a letter to your American colleague to 1)Express your thanks for his / her warm reception; 2)Welcome him / her to visit China in due course. You should write about 100 words on ANSWER SHEET 2. Do not sign your own name at the end of the letter. Use "Zhang Wei" instead. Do not write your address.