问题补充：
I’m writing this letter my mother, who wants to thank you for your nice gift.
A. in order to
B. in behalf of
C. on behalf of
D. in terms of
答案：
A. in order to
B. in behalf of
(答案→)C. on behalf of
D. in terms of
解析：词义辨析题。A. in order to为了 C. on behalf of代表D. in terms of 从…角度句意：我代表妈妈给你写信，妈妈感谢你的礼物。根据语境选C
