In general question will provide you an application context (mostly legacy application) and you need to answer what kind of J2EE technologies are suitable. Most importantly questions are attached to one or more non-functional requirements like performance, maintainability, manageability, scalability etc., So, your answer should address these requirements. Another type of questions just touch up on functional requirements of J2EE technologies.
Example for functional Requirement: you can use a stateless session bean if you do not need to store states specific to one client.
Example for non-functional Requirement: Use a DAO
pattern in case an application using BMP needs loose couping.