GMAT Sentence Correction (SC) | Re: Based on eyewitness accounts, claims of photographic evidence, and

The version created using choice A starts with the opening modifier, "Based on eyewitness accounts ..."

Following that opening modifier, there is nothing that is actually "Based on eyewitness accounts ...'

In other words, the opening modifier is a noun modifier, and the noun that follows it is "conspiracy theorists". Conspiracy theorists would not be based on accounts, and there is no logical target of the modifier in the sentence.
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