GMAT Sentence Correction (SC) | Scientists have observed pig cells in the culture producing

Right. Thanks.
But what about the rule that states that if there is no comma preceeding the verb-ing modifier then it modifies the closest noun.

So isn't culture a noun? Yes it is preceeded with "in " preposition. But that can only make sure that culture is not a subject as subjects r not preceeded byprepositions

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