Verbal Reasoning

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


guys, i ruled out options B,C,D but was stuck between A and E. Now i ruled out E because i could not find anything to which "it" in option E refers to. Can anyone tell me, what "it" refers to in option E

also i more query had it been that there was not comma after "until almost 1900" whether ambiguity in option would have been removed ?