Where a Person Who Is Really Acting as Agent for Another

Where a person who is really acting as agent for another does not tell this to a third party and enters into a contract with the third party,the third party

A) can only sue the agent,whether or not the principal is disclosed.
B) must decide whether to sue the agent or the principal.
C) can argue a mistake rendering the contract voidable at the third party's option.
D) can only sue the undisclosed principal,but not the agent.
E) must attempt to limit its losses by rescinding the contract.