Sentence Correction

Researchers are studying plastics that dissolve at different rates, and they are finding that the so-called "quick disintegration" plastics are taking more time to deteriorate than they originally seemed.

A. they originally seemed
B. they seemed originally
C. it seemed that they would originally
D. it originally seemed
E. it originally seemed they would

my concern: i have a little problem in understanding the answer to this question (proclaimed answer is E)
FIRSTLY: if i go by the logic of ellipses then E would be as follow: Researchers are studying plastics that dissolve at different rates, and they are finding that the so-called "quick disintegration" plastics are taking more time to deteriorate than it originally seemed they would [TAKE]----------->now what i am not able to understand is that no where in the previous clause is "TAKE" mentioned so how can we assume it in ellipses?

SECONDLY how "it" in E is expletive, if at all it is, as it is neither followed by "that" clause to "to phrase"

THIRDLY: if i take ellipses in A then won't A be also good choice?
A says: Researchers are studying plastics that dissolve at different rates, and they are finding that the so-called "quick disintegration" plastics are taking more time to deteriorate than they originally seemed [WOULD TAKE] ----------> what is preventing me to assume this ellipses?

thanks

The OA implies the following:
The plastics are taking more time...than it originally seemed they would [take].
The omitted word in brackets -- take -- is a verb form.
Generally, a verb form on the GMAT may be omitted only if it has appeared earlier in the sentence.
Here, the preceding verb form is taking.
Since the omitted verb form (take) is different from the preceding verb form (taking), the ellipsis in the OA seems invalid.