Which body is NOT considered an interinstitutional body of the EU?

The Council of the European Union is indeed considered an interinstitutional body of the EU, which makes it the correct association in terms of its role and function. It represents the member states' governments and is responsible for adopting EU legislation and coordinating policies.

In contrast, the European School of Administration, the European Personnel Selection Office, and the Computer Emergency Response Team (CERT-EU) do not hold the same level of intergovernmental significance or legislative authority as the Council does. The European School of Administration provides training for EU civil servants, the European Personnel Selection Office manages recruitment for EU institutions, and CERT-EU is focused on cybersecurity coordination within the EU. Therefore, these bodies operate in different capacities and do not serve the same central legislative and policymaking functions inherent to the interinstitutional framework of the EU, which is epitomized by the work of the Council of the European Union.