Which doctrine is associated with Apparent Authority?

Apparent authority refers to a situation where a third party reasonably believes that an agent has the authority to act on behalf of a principal, even if the agent does not have actual authority. The estoppel doctrine is pivotal in this context as it prevents a principal from denying the existence of authority when the third party has relied on the conduct of the principal that led them to believe that the agent had authority. Essentially, if a principal acts in such a way that leads others to believe an agent has authority, they cannot later argue against that authority if the third party has made decisions based on that belief.

The estoppel doctrine helps maintain fairness and protects the interests of third parties who may otherwise suffer harm due to the unqualified nature of the principal's representation of the agent's authority. It enforces the idea that principals must be careful and consistent in how they present their agents to the outside world. Thus, the correct answer effectively illustrates this fundamental principle in agency law regarding the scope of authority and the expectations of third parties dealing with agents.