5. What makes the following sentence unclear? He wanted to compete in the singing audition and win a music scholarship, but he didn't. It's a complex sentence and therefore does not need a comma. The two parts of the sentence are not parallel in structure. Since there is no independent clause, the sentence is incomplete. The sentence includes too many details to work as one sentence.

The correct answer is: The two parts of the sentence are not parallel in structure.<br /><br />Explanation: The sentence "He wanted to compete in the singing audition and win a music scholarship, but he didn't." is unclear because the two parts of the sentence are not parallel in structure. The first part "He wanted to compete in the singing audition and win a music scholarship" is a compound action, while the second part "but he didn't" is a simple negative statement. To make the sentence clearer, it could be revised to: "He wanted to compete in the singing audition and win a music scholarship, but he didn't succeed."