Answer:
D.) As appropriate for the topic and concern
Explanation:
Conference is a term that is used to describe a meeting of two or multiple people. The purpose of the meeting is commonly based on a specific topic and concern.
Usually, it takes a formal structure, settings, and tones. Sometimes it can last for days. It is often done externally such as in conference centers.
For example, academic conferences, business conferences, etc.
Hence, Conferences should be handled: "As appropriate for the topic and concern."