Final answer:
The correct option is A, which punctuates the dialogue with proper structure, indicating Wilson's whispered speech and his desire for a single chance to prove himself.
Step-by-step explanation:
The correct sentence that punctuates the given dialogue properly is: "I just want a chance," Wilson said, his voice barely a whisper. "Just one chance to show everyone that I'm not a loser." This sentence correctly attributes the dialogue to Wilson and uses proper punctuation, such as a comma after 'chance' and period inside the final quotation marks, to capture the break in his speech while maintaining the sentence structure. It conveys that Wilson spoke in a whisper and emphasizes the fact that he barely spoke. By doing so, it accurately conveys both the dialogue and the manner in which it was said, with Wilson's hope for a single opportunity to prove himself.