(A) in addition to its possibilities for preventing and inhibiting
(B) in addition to its possibilities to prevent or inhibit
(C) besides the possibility that it prevents and inhibits
(D) besides the possible preventing and inhibiting of

This sentence makes the outrageous statement that 'possible' preventing and inhibiting... (read literally anyways)

(E) besides possibly preventing or inhibiting (Correct)

One thing that I am not quite clear on is idiom choice here. "In addition to" vs "Besides"...I initially thought the former was correct as I've seen examples where besides was taken to be unidiomatic for the reason that it suggests something along the lines of "X being beside Y physically". Can someone chime one?

Can someone help me understand why D is wrong

Could you please re-read the thread? I think this is explained in several posts on previous three pages.
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But I still don't get it why "the preventing of" is wrong verb.

Options A,B & C have pronoun antecedent error and between choice D and E, E is more clear.

1) Many community reply in the post suggests that option A, B & C are eliminated as use of "its" for plural subject, but its can also refer to "tea" in the first clause or "camellia sinensis" in the same clause.
2) Could you please share the exact POE for this question ?

Hi aarkay87, in a clause, when a pronoun appears as part of introductory modifier, the pronoun refers to the noun immediately after the introductory modifier.

Here, the clause is:

in addition to its possibilities for preventing and inhibiting some forms of cancer, the brewed leaves of Camellia sinensis may also....

We have the following introductory modifier here: in addition to its possibilities for preventing and inhibiting some forms of cancer.

So, the pronoun its will refer to the brewed leaves, the noun immediately after the introductory modifier. However, the issue is that its is singular, while brewed leaves is plural.

p.s. Our book EducationAisle Sentence Correction Nirvana discusses this concept of Pronouns in Introductory modifiers. Have attached the corresponding section of the book, for your reference.

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Can this question go like, the clause after the semi colon is describing the the "tea", and later tits compares it with "brewed leaves"? I am being told to ignore the punctuations, although not sure to ignore as important as semi colon