a scentence correction -- scientists' believe

Dear All,

Here is a sentence correction, including lots of grammar knowledge: Wow~~~ big challenge for me...
Welcome to discuss it with me. Comon everybody. if miss something, please complete it...

Let's discuss the grammar as many as possible in stead of limiting the correct answer. yes, correct answer is the key to do good job on GMAT, why not enjoy the knowledge rather than only select a correct

Until Antoine Lavoisier proved otherwise in the eighteenth century, many scientists had believed that combustion released phlogiston, an imaginary substance whose properties were not fully understood.
A. many scientists had believed that combustion released phlogiston, an imaginary substance whose properties were not fully understood.
Tense
"had believed" is perfect past, implies verb "believe" happened before "proved", I got an idea that if the sequence of two past events is clearly indicated, then the use of past perfect is unnecessary, of course, scientist's believe happened before AL proved, thus, that means simple past "believed" will be better than perfect past "had believed"? sometimes I can't reflect immediately which tense will be better.
Modifier
an imaginary substance modify the noun "phlogiston", extended to all modifiers, how to identify which is be modified the whole preceding sentence or the preceding word, or there is a possibility modifier the latter sentence or latter noun?
whose
whose shouldn't modify people(from manhattan)? or it can modify not only people but also things, if it can, then, any restricted noun?

B. many scientists believed that phlogiston was an imaginary substance released by combustion and its properties were not fully understood
passive voice
released is switched to passive voice, seems no problem.
parallelism
because the word "and" introduced a parallelism,
first half "phlogiston was an imaginary...." and second half "its properties were not fully understood" are parallelism,
both two parts need not to use same voice, right? any rules introduce when they should be same voice?
its
its refers to phlogiston, right? there are two nouns appears , phlogiston and combustion, since combustion is action noun, is a procedure, these kind of nouns won't present a property, thus, "its" only refers to phlogiston,
if it is, as mentioned above, first part is action voice, second is passive voice, so its only refers to combustion,
ohhh, paradox happened....confused, seems "its" is not good to happen here..
one more shortage of grammar that I am not sure how to identified the reference of the pronouns, any rules here
until
if the word "until" introduce a clause, does it mean past perfect will be better than simple past?

C. phlogiston was an imaginary substance whose properties were not fully understood and which many scientists to be released by combustion
illogical
until...., phlogiston was an imaginary substance....., it doesn't make sense. Will phlogiston change its substance in different time era?
whose
"whose" refers to substance and introduces a clause
parallelism
and is a tag that two parts should be parallelism, while the second and the first are not paralleled,
which
I remember that which cannot introduce a clause, right? I am not sure where I read, or maybe I memory is incorrect.
sometime I am not confused with "that", "comma + which", "which", please help
I met a problem, I think I need some time to find the example

D. phlogiston, an imaginary substance whose properties were not fully understood, was believed by scientists to be released by combustion
noun + whose clause
noun + noun modifier
excerpt some rules from Manhattan,
1. Can more the absolute phrase to the end of the sentence, but cannot move the normal noun

(not clear about "can not move the normal noun")

2. Provides a way to link a second part of the sentence to the first
3. Never use which (which must refer the main noun and closet to the noun),

but can use which/whose/that to modifies the noun, right?

4. No this or that, if need, add an absolute phrases or another legitimate way to refer to previous thought
5. Another legitimate way is an " V ing" with comma, or dash
was believed by scientists to be released by combustion
I am not sure whether the issue here, but feel bad idiom, and have no idea how to correct it, any one help?

E. many scientists had believed that phlogiston was released by combustion and was an imaginary substance whose properties were not fully understood.
Tense
had believed
parallelism
was released by combustion
was an imaginary substance whose properties were not fully understood.

seems A and E are no problem, but it won't happen, I have no idea how to select A or E, wow~~, anyone help me?

ok, long analyze, hahaha...
thanks that you spend sometime to read, I believe there are some issues, including my sentence error,
Please correct them or complete them >_~

thanks a lot,
have a nice day.

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