Which sentence must be revised to eliminate the preposition at the end?

In choice C, “to” is a preposition left at the end of the question. Revise it to “To where are Katelyn and Ella walking?” or, more naturally, “Where are Katelyn and Ella going?” The other choices do not end with a preposition: “in” in A and “below” in B are not stranded at the end, while “about” in D is part of the phrase “talking about” but is not the sentence’s final word.

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