2012考研必备：考研英语语法精要(22)

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2.表示虚拟语气
    (1)needn’t have+过去分词，表示做了不必做的事，译为“其实没必要……”。如：
    As it turned out to be a small house party, we needn’t have dressed up so formally.
    (2)should /should not have +过去分词，表示应该做某事但实际上未做，或本不应该做但实际上做了, 译为“本(不)应该……”。如：
    I regret having left the work unfinished; I should have planned everything ahead carefully.
    (3)ought to have+过去分词，表示动作按理该发生了，但实际上未发生，译为“该……”，与should的完成式含义类似。如：
    The porter ought to have called the fire-brigade as soon as he saw the fire in the stock, which went up in smoke.
    (4)could have+过去分词，表示过去本来可以做但却未做，译为“完全可以……”。如：
    What you said is right, but you could have phrased it more tactfully.
    (5)may/might have + 过去分词，表示过去可以做但实际未做，译为“(那样)也许会……”。如：
    It might have been better to include more punchy statistics and photos of equipment in the introduction to further assist first-time office automation managers.