Lee, an overseas student from China, once had a talk with his Am

Lee, an overseas student from China, once had a talk with his American classmate Tom.
Lee: It really puzzles me that you Americans thank people all day long. When the teacher answers your questions, when your mother buys you a book that you need, when a wife brings her husband a cup of coffee and so on.
Tom: Well, when I finished my tour in China, I said "thank you" to the interpreter who accompanied me during the tour. The interpreter replied, "It's my duty to do so.'I can't help thinking what he means, "I had no choice but to do it, because it is my duty.Otherwise I would not have done so."
Questions: (1) What makes Lee puzzled and why?
(2) Is the interpreter's reply appropriate in the English context?
【正确答案】：1)A Chinese student would always thank his/her teacher for the latter's help, but would seldom do so to his/her parents because Chinese people don't usually say"Thank you" to those who are very close. They would rather choose some implicit ways to show their gratitude and concern, such as saying something like "l累了吧?", "辛苦了", "快歇歇吧" etc. But one traditional Chinese concept holds that it is the duty of the young and the junior to do something for the elderly and the senior, and so the latter don't have to say thanks.
Saying "Thank you" is very common in America, even between parents and children, husband and wife for very small and ordinary things. So they thank all daylong. They use words like "Please", "Excuse me", "Thank you" in daily conversation,whether between intimates or between strangers.
2)Both English and Chinese cultures require their members to respond to thanks. But they have different expressions. The interpreter's reply was far from the message he/she actually intended to convey.