Which of the following statements is NOT true regarding ostensible agency and agency by estoppel?

This statement is true because agency by estoppel typically arises when a principal's actions lead a third party to reasonably believe that an agency relationship exists, which often requires the prior establishment of an ostensible agency environment. Thus, this choice correctly describes a relationship between the two agency concepts.

This choice is accurate as both agency by estoppel and ostensible agency can emerge without an express agreement. They can be invoked during various phases of a relationship, including times of uncertainty about the agency's status, making this statement true.

This statement is true and captures the essence of both agency by estoppel and ostensible agency, which fundamentally involve third-party perceptions. These concepts are defined by the misrepresentation of agency to third parties, hence it accurately reflects the nature of both agency forms.