First Principles Thinking: governing standard
B is correct. Standard VI(C) requires members and candidates to inform employer, clients, and prospective clients of benefits given or received for referrals. The competing principle is that the broker, as the person making the recommendation, may look like the only party who needs to speak. The hierarchy is that each member involved in the arrangement must satisfy his or her own disclosure obligations when dealing with the affected prospect. Because the manager knows the prospect came through a compensated referral arrangement, the manager cannot rely solely on the broker to make the disclosure. Thus, the assumption is unreasonable.
Why top distractor is tempting but wrong (missed nuance). Control of the first contact does not transfer away the manager's own duty once the manager engages the prospect under a known referral arrangement.
Why remaining distractor fails (boundary violation). Lack of an exact amount may affect how the value is estimated, but it does not remove the duty to disclose the existence and nature of the benefit.