Why is it important to fill out an interest inventory before searching for a job?

to make sure that you are qualified for the job that you choose

to practice filling out a form before you have to fill out job applications

to identify your strengths and preferences that you will take to a job

C. To identify your strengths and preferences that you will take to a job

I'd say definitely c. A doesn't work, its not about qualifications, b, not all job applications have forms, loads want cv's and anyway they aren't interested in teh same sort of thing. Having said that I'm not convinced they are that useful as you may discover your preferences and strengths are in wholly different areas.