Final answer:
The correct way to create an agency relationship is through establishment, which allows one person to authorize another to act legally on their behalf.
Step-by-step explanation:
An agency relationship is created through a process where one person, the principal, authorizes another, the agent, to engage in legal relations on their behalf. Among the options provided, the correct way to create an agency relationship is 3) Establishment. 'Eradication' and 'Expiration' are terms that are more associated with the ending of an agency. 'Estoppel' can prevent the principal from denying the existence of an agency if their actions have led others to believe it exists, but it isn't a method of deliberately establishing an agency.