Final answer:
The Longer Ending to Mark's Gospel was not defined as canonical by any of the Church Councils listed.
Step-by-step explanation:
The Longer Ending to Mark's Gospel, which includes verses 9-20, was not defined as canonical by any of the Church Councils listed in the options. It's important to note that the authenticity of the Longer Ending is disputed among scholars, and some consider it to be a later addition to the Gospel. The Council of Nicaea in 325 CE and the Council of Chalcedon in 451 CE primarily focused on theological debates surrounding the nature of Christ, rather than the canonicity of specific biblical passages. Therefore, none of the options provided are correct.