I think the answer is B: Charles Dickens; renames author.
An appositive are noun phrases placed side by side. That is the easiest way I could define it.
So, you have the noun Charles Dickens then what follows next is another noun that renames that noun that you just used, which in this case is renames author.
Grammar is WEIRD!!! :)
The appositive in the sentence is "Charles Dickens," which renames the noun "author." Therefore, the correct choice is B: Charles Dickens; renames author.
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