Which authority is considered when an agent can act based on the perception of third parties?

Apparent authority is the correct answer because it refers to the situation where a third party reasonably believes that an agent has the authority to act on behalf of a principal based on the conduct of the principal or the agent. This concept hinges on perceptions created by the principal's actions or communications, leading third parties to conclude that the agent is authorized to engage in certain transactions.

In this context, if a principal acts in a way that suggests to third parties that the agent has certain powers, the principal may be bound by the actions of the agent, as those third parties could reasonably rely on that perception when interacting with the agent. This type of authority operates on the idea of fairness, protecting third parties who may rely on such appearances in their dealings.

While express authority refers to specific powers granted to an agent in clear, explicit terms, and implied authority pertains to the powers that are not explicitly stated but are necessary to carry out the duties that are expressly granted, these do not primarily depend on the perceptions of third parties. Customary authority, although it relates to what is typical in a particular trade or industry, also does not focus on the perceptions of third parties in the same way that apparent authority does.