请教单选No.I don’t know the person who wrote it.There must be some _________.
问题描述：
请教单选No.I don’t know the person who wrote it.There must be some _________.
--Is this letter yours?
--No.I don’t know the person who wrote it.There must be some _________.
A.trouble\x05\x05B.development\x05C.mistake\x05 D.solution
答
C