Formal Adjudication in administrative law can best be described as:

Formal adjudication in administrative law is characterized as a comprehensive trial-like proceeding. This is because formal adjudication typically involves procedures similar to those found in a courtroom, including the presentation of evidence, witness testimonies, and a formal decision-making process by an administrative law judge or agency body. The goal of this type of adjudication is to ensure that disputes are resolved fairly and based on a clear record of the proceedings.

In formal adjudication, rules of procedure and evidence are often prescribed by law or regulation, reflecting the more structured environment resembling traditional judicial processes. This contrasts with the other options provided. For instance, processes without the need for a trial do not incorporate the rigorous evidentiary standards or due process protections inherent in formal adjudication. Informal mediation sessions are typically more collaborative and lack the adversarial nature of formal proceedings, while a legislative discussion format focuses on policy-making rather than resolving specific disputes through a formalized judicial-like process. Thus, B accurately captures the essence of formal adjudication as it exists within administrative law.