Sentence Correction

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


I went with B. but OA is E..... can somebody please help me understand this.?