Sentence Correction

Though now eaten in large quantities around the world and harmless, the tomato is a member of the generally toxic nightshade family, including belladonna, and was once thought to be poisonous itself as a result.

A) Though now eaten in large quantities around the world and harmless, the tomato is a member of the generally toxic nightshade family, including belladonna, and was once thought to be poisonous itself as a result.
B) The tomato, though now eaten in large quantities around the world and harmless, is a member of the generally toxic nightshade family, which includes belladonna, and it was therefore once thought to be poisonous itself.
C) Once thought to be poisonous itself, the tomato is harmless and now eaten in large quantities around the world, and is a member of the generally toxic nightshade family, including belladonna.
D) Though now eaten in large quantities around the world and known to be harmless, the tomato was once considered poisonous because it is a member of the generally toxic nightshade family, which includes belladonna.
E) A member of the generally toxic nightshade family, including belladonna, the tomato was once considered poisonous even though it is harmless and now eaten in large quantities around the world.

OA:D

I need help to understand the following:

1- Are 'eaten in large quantity...' and 'harmless' parallel with each other?
2- Manhattan "including belladonna" is wrong in Choice A , C & E? IS there any rule for using 'including'??

Mo2men wrote:Though now eaten in large quantities around the world and harmless, the tomato is a member of the generally toxic nightshade family, including belladonna, and was once thought to be poisonous itself as a result.

A) Though now eaten in large quantities around the world and harmless, the tomato is a member of the generally toxic nightshade family, including belladonna, and was once thought to be poisonous itself as a result.
B) The tomato, though now eaten in large quantities around the world and harmless, is a member of the generally toxic nightshade family, which includes belladonna, and it was therefore once thought to be poisonous itself.
C) Once thought to be poisonous itself, the tomato is harmless and now eaten in large quantities around the world, and is a member of the generally toxic nightshade family, including belladonna.
D) Though now eaten in large quantities around the world and known to be harmless, the tomato was once considered poisonous because it is a member of the generally toxic nightshade family, which includes belladonna.
E) A member of the generally toxic nightshade family, including belladonna, the tomato was once considered poisonous even though it is harmless and now eaten in large quantities around the world.

A and B: Though now...harmless
This wording implies that the tomato was once poisonous but now is harmless.
Not the intended meaning.
The intended meaning is that the tomato was once CONSIDERED poisonous but was not ACTUALLY poisonous.
Eliminate A and B.

2- Manhattan "including belladonna" is wrong in Choice A , C & E? IS there any rule for using 'including'??

COMMA + including must serve to introduce example(s) of a PRECEDING PLURAL NOUN.
Check my post here:
https://qa.www.beatthegmat.com/doubt-sc-t280864.html

C and E: a member of the generally toxic nightshade family, including belladonna.
Here, COMMA + including seems to refer to family (singular).
Since the referent for COMMA + including must be plural, eliminate C and E.

The correct answer is D.

1- Are 'eaten in large quantity...' and 'harmless' parallel with each other?

A participle (VERBed or VERBing) serving as an adjective may be considered parallel with a non-participle adjective.

An OA in GMATPrep:
For the farmer who takes care to keep them cool, provided with high-energy feed, and milked regularly, Holstein cows will produce an average of 2,275 gallons of milk each per year.
Here, provided and milked (VERBed participles serving as adjectives) are considered parallel with cool (a non-participle adjective).

OG16, page 42, SC44:
Seldom more than 40 feet wide or 12 feet deep but running 363 miles across the rugged wilderness of upstate New York, the Erie Canal connected the Hudson River at Albany to the Great Lakes at Buffalo.
Here, running (a VERBing participle serving as an adjective) is considered parallel with wide (a non-participle adjective).

Given these OAs, I would not consider eaten and harmless an error of parallelism.
That said, the parallelism in D is superior:
D: Though now eaten in large quantities around the world and known to be harmless
Here, eaten (past participle) is parallel with known (past participle).
Since the two modifiers are both verb forms, the result is superior parallelism.