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题库 / OG12-SC-3
Although various eighteenth- and nineteenth-century American poets had professed an interest in Native American poetry and had pretended to imitate Native American forms in their own works, until almost 1900, scholars and critics did not begin seriously to study traditional Native American poetry in native languages.
until almost 1900, scholars and critics did not begin seriously to study
until almost 1900 scholars and critics had not begun seriously studying
not until almost 1900 were scholars and critics to begin seriously to study
it was not almost until 1900 when scholars and critics began to seriously study
it was not until almost 1900 that scholars and critics seriously began studying
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根据原文可知study这个动作在之前就存在，只不过是到了1900年开始seriously。属于状态的持续而不是转变，故用doing而不是to do
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