Here are the matches:
1. That reminds me,... - E
2. Why don't we... - I
3. I'd better get going... - G
4. Thanks for your letter... - C
5. Please let me know... - J
6. I'm really sorry... - B
7. Love, - H
8. Could you do something for me? - F
9. Write soon... - D
10. Did you know that.. - K
11. I'm happy to hear that... - A