Final answer:
Authority granted after an act has already been performed is known as ratification, which is not one of the options provided. Among the available choices, implied authority is the closest, although it generally refers to authority assumed to exist rather than granted retroactively. The correct option is a.
Step-by-step explanation:
The term authority in the context provided refers to the power granted to a person or organization to act on behalf of another. In business and legal settings, this often pertains to the relationship between a principal and an agent and decisions made therein.
When authority is provided after an action has already been taken, it is generally referred to as ratification, which is not one of the options provided in the question. However, among the given choices, none directly refer to ratification or authority given after an act.
The closest related term would be implied authority, although it commonly refers to authority that is not expressly granted but is assumed to be provided due to the nature of the relationship or actions of the parties involved, rather than being granted retroactively.
None of the options presented as A (Implied authority), B (Express authority), C (Dual agency), or D (Subagent) strictly fits the description of authority approved after an act, but implied authority comes closest when no option for ratification is offered. The correct option is a.