Which of the following is true about the criminal liability of a corporation and its officers?

a$.$ Officers and directors, as in the case of agents, cannot be held personally responsible for any crimes committed by them.

b$.$ Officers and directors, as in the case of agents, cannot be held personally responsible for any crimes committed by them if they acted on behalf of the corporation.

c$.$ A corporation itself may be convicted of a criminal offense if its agent committed the offense acting within the scope of the agent's authority.

d$.$ Officers and directors can only be held criminally liable at the local and state level.