Which of the following best describes an advisory letter?

An advisory letter serves to communicate the results of an investigation, particularly when those results do not necessitate any further action or penalties. The key characteristic of an advisory letter is its function as a notification, which helps inform the involved parties about the conclusions reached, while also clarifying that there are no immediate obligations or repercussions stemming from these findings.

This type of correspondence is commonly used in various professional and regulatory settings to maintain transparency and keep stakeholders informed about matters that may affect them, without signaling the need for corrective measures. Its role is therefore inherently about guidance and information rather than reprimand or formal charges, which distinguishes it from the other options presented.