Final answer:
The correct sentence uses a colon to introduce an explanation.
Step-by-step explanation:
The sentence that uses a colon correctly is: The day felt like a long winding road: it seemed as if it would never be over. A colon is used to introduce an explanation, example, or list, and in this sentence, the colon is correctly used to introduce the explanation of why the day felt like a long winding road.
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