Enthuware

Isn't it mandatory, when a session bean implements an interface that is not Serializable, to either specify it in @Local(..) or @Remote(...), or have the interface annotated with @Local or @Remote, or have the @LocalBean annotation?

This makes the correct answer incomplete.

No, as per section 4.9.7:

If the bean does not expose any other business interfaces (Local, Remote) or No-Interface view, and the bean class implements a single interface, that interface is assumed to be the business interface of the bean.

HTH,
Paul.

Yes. ... thank you very much for your answer! I overlooked that aspect

I also appreciate the quality of the questions, answers and explanations for this exam!