Explanation

This question is an excellent lesson in the principle, “Don’t add anything to your reading of the sentence that wasn’t there already.” What were you told? Just that the first short story collection had many diverse voices, and the second collection has “a ________ narrator” — in other words, just one speaker.
Therefore, you don’t know that the stories or narrator are insightful, facetious, lonely, or disingenuous.

Motley, even, sole.
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Sandy
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Yes but motley in the sense of incongruously, disparate.

A is more suitable here in the context.

Regards
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