In Which of the Following Circumstances Will an Agent's Act

In which of the following circumstances will an agent's act not generally be binding on the principal because the agent has no authority (leaving aside contexts in which the agent has apparent authority) ?

A) When the agent was given verbal authority by the principal to do the act.
B) When the principal has ratified the act verbally.
C) When the act was something necessary or appropriate given the scope of the agent's actual authority although they had no express authority.
D) When the agent's authority was given verbally in circumstances in which legislation required the authority to be given in writing.