The largest trade-book publisher in the US has announced the creation of a new digital imprint division, under which it will publish about 20 purely digital works to be sold online as either electronic books or downloadable copies that can be printed upon purchase.

A) works to be sold online as either electronic books or
B) works to sell them online, either as electronic books or
C) works and it will sell them online as either electronic books or as
D) works, and selling them online as either electronic books or as
E) works, and it will sell them online as either electronic books or

This is a GMAT Prep question

My question is :- A " works to be sold online as either electronic books " how "to be" connects works , that is how it modifies works . Frist look it is passive voice

and in E it is catchy as "it will publish about 20 purely digital works , and it will sell them online as either electronic books or" seems parallel connect by co-ordinating conjuction. Then why A is correct and E is wrong? May be under which be wrongly interpreted for " under which <a new digital imprint division> it will sell them online as either electronic books

your last sentence is spot on: e is wrong because it changes the meaning of the sentence.
* the original - which, remember, you can't change unless it's total nonsense - says that the publisher is making things which will subsequently be sold online, but it doesn't say by whom.
* choice e, on the other hand, asserts that the publisher itself is going to sell the things. that's an immense change in meaning (and moreover, how many publishers sell their own books online?).

you are also correct that the construction 'to be sold' is passive voice. in fact, the passive voice is necessary here, because you don't know who is going to be selling the books. (compare the analogous sentence 'there is still plenty of food left to be eaten').

Is there any issue with the or vs. or as at the end of the sentence? I used this as a split and marked out anything with "or as" because it there is no as before downloadable copies.

the issue is the parallelism required by the 'either ... or' construction. in particular, because that construction has a leading word ('either'), it involves two clearly defined parts: the words coming between 'either' and 'or', and the words coming after 'or'. those two parts must have exactly the same grammatical construction.

so, the following are acceptable:
either as electronic books or as downloadable copies
as either electronic books or downloadable copies

the following are not acceptable:
as either electronic books or as downloadable copies (one 'as' outside, one inside)
either as electronic books or downloadable copies (one 'as' present, one absent)

you get the idea.

works, and it will sell them ..

if the activities were parallel ... we would not need the comma..suggesting a new clause...

is this interpretation correct ??

I'd also say D and E are wrong because of the comma. The comma makes them a non-essential clause, and these statements are essential to the statement. Is this accurate?