The correct answer is A. Adversarial process. In an adversarial system, the parties are primarily responsible for investigating the case, gathering evidence, presenting proof, and examining witnesses. Their lawyers drive the presentation of the case, while the judge usually serves as a neutral decision-maker who oversees procedure, rules on objections, and applies the law. This description matches the facts in the question exactly.

By contrast, an inquisitorial process generally gives the judge a much more active role in developing the factual record, directing the inquiry, and often controlling much of the witness examination. That is why option B is not the best fit. Option C, civil law process, refers to a broad family of legal systems and is not the precise procedural label for the fact pattern described. Option D, unitary process, is not the recognized term used here. The CFE Law materials treat this distinction as a fundamental comparison between the two major procedural models: adversarial systems rely heavily on party presentation, while inquisitorial systems rely more heavily on judicial investigation. Therefore, because the parties gather the evidence and conduct the questioning, A is the most accurate answer. The CFE exam outline also distinguishes these procedural frameworks within the Law section.