In this question, why couldn't it also fall under the "admission" exception to the hearsay rule, and therefore be answer A?

A plaintiff sued a defendant for illegal discrimination, claiming that the defendant fired him because of his race. At trial, the plaintiff called a witness, expecting him to testify that the defendant had admitted the racial motivation. Instead, the witness testified that the defendant said that he had fired the plaintiff because of his frequent absenteeism. While the witness is still on the stand, the plaintiff offers a properly authenticated secret tape recording he had made at a meeting with the witness in which the witness related the defendant's admissions of racial motivation. The tape recording is admissible as evidence of the defendant's racial motivation and to impeach the witness's testimony. n admissible only to impeach the witness's testimony. inadmissible, because it is hearsay not within any exception. D inadmissible, because a secret recording is an invasion of the witness's right of privacy under the U.S. Constitution