Necessary to any investigation of the causes of a newly-discovered dis

Dear Sir,

Is .... are a necessity of any investigation "into" the causes of a newly discovered disease incorrect??

I could not find definitive error points to scrap "D"

Bunuel generis
Experts please help us with explanation

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itoyj My take on it:

Necessary to any investigation of the causes of a newly-discovered disease are strictly followed scientific methodologies and scrupulously recorded data.

A) Necessary to any investigation of
-- "Necessary to any investigation of the Xs are As and B"
-- Sounds ok, leave it for now

B) It is necessary in making any investigation into
-- "It" = ? Presumably it's something like "components" but the pronoun is the wrong plurality
-- "in making any investigation" is wordy, you just say "investigating" (and anyway, how do you 'make' an investigation?)
-- worst offender: singular "is" when we have plural "are" later in the sentence, you get "It is necessary in making any investigation into the Xs ... are As and B"

C) When making any investigation, it is a necessity of
-- same issues as above

D) A necessity of any investigation into
E) A necessary part of investigating into
-- Again, "necessity" and "necessary part" does not match with the plural "are" later on

So, If you truncate the sentence you get "A necessity/A necessary part" of Xs ... are As and Bs"

Best way to approach such problems is to shorten down the sentence. Here:

Necessary to any investigation of the causes of a newly-discovered disease are strictly followed scientific methodologies and scrupulously recorded data.

After Shortening:

Necessary are

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