Where must the certificate be displayed when conducting business?

The certificate must be displayed for the customers to ensure transparency and trust. When it is visible, it indicates that the business is authorized to conduct inspections and adheres to the required regulations. This visibility reassures customers that they are dealing with a legitimate service provider, which is crucial in maintaining compliance with state regulations regarding vehicle inspections. A well-placed certificate serves as a clear endorsement of the service's credibility.

While the other options may suggest places where documents could potentially be stored or displayed, they do not fulfill the requirement of being directly visible to customers. Being posted in the inspection area, for example, might not be fully accessible to the public, and keeping it in a file cabinet or behind a counter would not allow customers to see it at all. The focus is on customer interaction and ensuring they are informed about the qualifications of the service they are receiving.