Use of style merely suggests the writer could influence readers through range of characters as highlighted.Whereas,modulation and nuances fits best to bring variation/gradation to the style,tone and diction for a great writer to take readers in and out of the vernacular of characters as different as an Appalachian college freshman, a visiting professor from Cambridge, and an Italian-American Brooklyn police officer.

B and F

Every sentence has a CLUE -- a portion that indicates the required meaning for the blank.
Whenever possible, recycle the clue by inserting it directly into the blank.

Here, the clue is how a great writer can take readers in and out of the everyday speech of very DIFFERENT characters.
Since the clue is about DIFFERENT speech patterns, recycle the clue by inserting the word differences into the blank.
Of the six options, only B and F refer to differences.

Modulation and nuances

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