--She didn't pass the exam yesterday.
--She _____ it well.A.must have preparedB.should have preparedC.must have prepared forD.should have prepared for
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D解析prepare sth. 表示准备手头上的事，暗示所需时间甚短：“prepare for sth.”表示为某事在事前做好准备工作，暗示所需准备的时间较长。“为考试事前做好准备”，要用prepare for sth. should have prepared for the exam意为“本应当为考试做好一切准备(实际上却未做)”，含有较强的责备意味。