You must have read about Mark Twain long ago, ?
A. mustn't you
B. haven't you
C. didn't you
D. needn't you
网友回答
A. mustn't you
B. haven't you
(答案→)C. didn't you
D. needn't you
解析：考查反义疑问句。句中must have done 表示对过去的肯定推测，而且有明显的时间状语long ago。做反义疑问句时用助动词did，所以答案选C。