28. ---- Who told you my email address?
---- I don’t remember clearly. It Karen.
---- It Karen. She doesn’t know my email address.
A. may have been; can’t have been
B. must have been; mustn’t have been
C. may have been; must have been
D. must have been; mustn’t be
网友回答
(答案→)A. may have been; can’t have been
B. must have been; mustn’t have been
C. may have been; must have been
D. must have been; mustn’t be
解析：根据题意“I don’t remember”可知第一空是要表达“可能是Karen
的）”；又根据“She doesn’t know my email address. ”可知说话人认为“不可能是Karen.”.