为什么是thank you (for) your letter

为什么是thank you (for) your letter 为什么是thank you for not smoking而不用no? thank you for your nice present.______为什么是I'M VERY GLAD YOU LIKE IT而不是YOU'RE WELCOME Thank you for you Thank you very much for helping us.答句为什么是Not at all?You are so kind不行吗? 什么是举一反三?THANK YOU Thank for you help. thank you for the Thank you for thank you for your thank you for the Thank you for your thank you for Thank you for this Thank you for killing thank you for leaving thank you for missing thank you for help