Which of the following sentences demonstrates correct colon usage with explanation?

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The sentence "He had one thing on his mind: winning the championship" demonstrates correct colon usage because it effectively uses the colon to introduce an explanation or elaboration of the first part of the sentence. The first part sets up an expectation—the idea that he is focused on something specific—and the colon signals that what follows will clarify or complete that thought.

In this case, "winning the championship" is directly related to the preceding clause and provides the necessary detail about what that "one thing" is. The structure is appropriate, as colons are most often used to introduce lists, quotes, explanations, or conclusions that follow logically from the preceding clause. The connection between the two parts of the sentence maintains clear communication and adds to the reader's understanding.