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

a) if no one answers the door, then let yourself in.
b) the top steps are fine, but be careful of the slippery stairs below.
c) where are katelyn and ella walking to?
d) do you know what naveen was talking about?

C) Where are Katelyn and Ella walking to? is the correct answer

The sentence must be revised to eliminate the preposition at the end is "Where are Katelyn and Ella walking to?"

Explanation:

The sentence that must be revised to eliminate the preposition at the ends is option C since it is impossible to eliminate the preposition from the other sentences, doing this would leave them incomplete and they will not have a full message, on the other hand, option C can work in both was, this question can be made with or without the preposition at the end but it will have different meanings.

"the sandy walls seemed to collapse in on themselves"

and

"the bloodshot waters seemed to have no bottom"

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explanation: