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题库 / Prep2007E2-SC-8
Ozone, a special form of oxygen that screens out harmful ultraviolet rays, reaches high concentrations twelve miles above Earth, where it has long appeared that it was immune from human influence; we have now realized, though, that emissions of industrial chlorofluorocarbons deplete the ozone layer.
has long appeared that it was immune from
has long appeared to have been immune from
has long appeared as being immune to
had long appeared immune to
had long appeared that it was immune to
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immune to； immune from，前者是对···免疫；后者是免除于····；排除AB；
as being immune to 这种说法太wordy了，GMAT要求语言简练，直接排除C；类似的题目还有很多；
剩下DE；
seem，appear，look，feel，smell，sound，taste是系动词，后面可以直接跟形容词；D很简洁又正确；
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