The methos execute without a transaction or What? What is dhe default behavior?
In case you did not specify transction type for CMT beans, the default type will be used. However, different containers will have different default types, and thus, you have to check the documentation of the container to obtain the default behaviour.
The exam is all about your understanding of the EJB spec, so remove from your memory anything which is vendor-specific.
Returning to transaction attributes: you shouldalways specify them. If you allow the EJB Server to provide a default attribute of Supports, this is really asking for trouble and should, in my opinion, never be used. So, for the exam, learn about Supports but keep away from it in the real world!