Many literary critics consider James Joyce’s Ulysses (1922),
a novel once banned as an obscene one, as the greatest novel of the twentieth century due to its remarkable synthesis of mythology, philosophy, and social realism.
We need to make a choice between Consider X as Y vs Consider X to be Y split.
Though Consider X Y is preferred choice but here we don't have that option.
Second is the modifier of Ulysses. In each option we have some variations, so lets check them -
(A) a novel once banned as an obscene one, as - Incorrect
once banned as an obscene one - one is redundant
(B) which is a novel that was once banned as obscene, as
no issues but it is wordier because of using 'which is'
(C) once banned for its obscenity as a novel, to be - Incorrect
was it banned for its obscenity because it was a novel? meaning is distorted here.
(D) once a banned and obscene novel, to be
Parallelism - once a banned novel and once a obscene novel - so is it not obscene now? - Incorrect
(E) a novel once banned as obscene, to be
No issues
so between option B and E - I chose E as the modifier is more precise
Answer E