Who can blame a business for asking this question in regards to SEO. After all, that's what they're paying for...results. This article is accurately sums up the answer (or lack there of). There are no absolutes when it somes to SEO because you are chasing something that wants to stay hidden and will change as soon as it feels it's been figured out - the algorithm.

My recommendation for any SEO company or specialist is to sell the reality of SEO. There's no secret magic to SEO, just technical know how and proven tactics. (both things few businesses have when it comes to websites and search engines).