How to answer
Were you attracted to the job posting because the company culture was enticing? Did they suggest an irresistible compensation package? Perhaps you know about the company's reputation and it prompted you to apply. Tell the hiring manager how you felt when you initially saw the job posting.
"I was really excited when I first saw your job posting because I have had an eye out for openings in your company for quite some time. Your organization has a very strong reputation and when I read the posting, it described the exact role I have been looking for. I applied immediately and am thrilled to be here interviewing with you today."