OG 12 SC-003 A选项的夹心结构，看了几十张贴，没有找到这个问题。。。

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.

(A) until almost 1900, scholars and critics did not begin seriously to study
(B) until almost 1900 scholars and critics had not begun seriously studying
(C) not until almost 1900 were scholars and critics to begin seriously to study
(D) it was not almost until 1900 when scholars and critics began to seriously study
(E) it was not until almost 1900 that scholars and critics seriously began studying

问题1：插入语和grammatical fragments如何区分呢？我第一眼看到A选项，排除的理由竟然是fragments...
问题2：OG上说A选项中的“until almost 1900” 既可以修饰although从句中的动作，又可以修饰后面主句中的动作，从而造成修饰的ambiguous。一方面，我觉得前一句中的主语是eighteenth and nineteenth-century American poets, 从语义上来讲，until almost 1900 不太可能去修饰17,18世纪的人。另一方面，像“until almost 1900”这种结构一般都是放在句首修饰主句，不太可能单独地放在句尾修饰前面的动作，所以就不会出现修饰的ambiguous问题。