13. When she was in trouble, I did what I could to help her. my help, she wrote me a letter of thanks.
A
In honor of
B
In case of
C
In terms of
D
In return for
句意为：她遇到困难时候，我尽我所能帮助她，为了感谢我，他写了一封信。A尊重B万一C提到D作为回报。所以选择D。
此题是固定搭配辨析，首先要明确句意，其次判断缺位词组。
词组意思。