I own stock in that company and have no idea who the CEO is. A clerk in that store probably wouldn't, either. The answer is that you'd treat the CEO like any other customer and help him or her find whatever they're looking for.
I answered consistently and thought carefully Before I answered (remember customer is always right good customer service and be able to meet qualifications)
I would refer to the ones I know by name; for instance, 'Good morning Mr. Brown. How may I assist you today.' If I don't know them by name, I would simply refer to them respectfully as sir or ma'am as deemed appropriate.
The interviewers inquired about my first impression of their office. That is like asking someone how nice of a car your old jalopy might be! Not very impressive to be thrust into a bunch of cubicles upon entering the door. Considering it was a sales office, no sales activity or phone calls were being made to prospects. Nothing state of the art, no equipment other than a few headsets and moderately aged computers. And no receptionist or greeter at the front. The ONLY impressive things are the double wooden doors. It's unfortunate that those same doors lead to nowhere. The only occasional workers to be seen appeared staged. acting as "good employee/bad employee" for my viewing pleasure while I awaited the interviewers. The office almost gave the impression of a company that was providing a front for a non-existent company.