a thank-you letter的用法和样例：
- She walked away without so much as a thank you.
- She took the money without so much as a thank you.
- Reuben murmured a thank you and ran home.
- A Thank you very much. I had a great drive from Los Angeles.
- She always writes thank you letters after her birthday.
- A： Thank you very much, Mr. Cohen. I'll be waiting for your reply.