The duality between
how Racine lived in the theatre and his life of faith and devotion should be seen not only as an internal division but also as a possible reason that Racine, in an age of optimism, selected tragedy as the preferred form.
A.how Racine lived in the theatre and his life of faith and devotion should be seen not only as
B.Racine’s life of the theatre and his life of faith and devotion should be seen as not only
C.theatrical life of Racine and his faithful and devotional life should be seen not only as
D.Racine’s life in the theatre and his life of faith and devotion should be seen not only as
E.Racine’s life of the theatre and his faithful and devotional life should be seen as not only
The sentence says that the duality between X and Y should be seen not only as A but also as B.
Here X must be || to Y and A must be parallel to B.
Now for A and B we can see that in the non underlined part of the sentence the strucure is but also as .Therefore A must have the same struc not only as A but also as Y.
So we know there must be an as at the end of the underlined part.
Eliminate B and E for the aforementioned reason.
Now let's deal X and Y.
Racine's life of(.faith and devotion......) is compared to his life in(...theatre)
So life with prepositional phrase is the structure .
D is the one that follows this structure.