A too-general answer that could apply to any position. You don’t want to give the impression that you’re only interested in this job because it’s available. I often compare job interviewing to dating (hopefully, dating is at least a little bit more fun for you). No date wants to hear, “You were the only one who would go out with me.” It’s the same with job interviewing. You have to woo the company and talk about why the position was made for you.
An uninformed answer that shows you don’t understand the job. If you don’t comprehend every word on that job description, take some time to research.
An unenthusiastic answer that makes the interviewer wonder if you really want the job. If you can’t provide details about why you’re into the job, the interviewer will likely assume that you’re NOT.