What must agents disclose to their principals?

The correct answer highlights the fundamental duty of agents to serve the best interests of their principals by disclosing all information that is relevant to the principal's interests in a transaction. This obligation is rooted in the fiduciary relationship between an agent and a principal, which requires agents to act loyally and in good faith. By ensuring that all pertinent information is shared, the agent helps the principal make informed decisions, thereby enhancing the trust inherent in their relationship.

In contrast, simply communicating only positive information would compromise the agent's duty to provide a full picture, potentially misleading the principal. Personal opinions, while they might provide subjective insights, are not necessarily relevant and fall outside the scope of mandatory disclosure unless they are directly related to the interests of the principal in the transaction. Lastly, disclosing information only upon explicit request can leave the principal uninformed about critical aspects that could affect their decision-making, undermining the agent's role and responsibilities.