Your web site has many user-customizable features， for example font and color preferences on web pages.Your IT department has already built a subsystem for user preferences using Java SE’s lang.util.prefspackage APIs and you have been ordered to reuse this subsystem in your web application. You need tocreate an event listener that stores the user’s Preference object when an HTTP session is created. Also，note that user identification information is stored in an HTTP cookie. 
Which partial listener class canaccomplish this goal？（）

You have a use case in your web application that adds several session-scoped attributes. At the end of theuse case， one of these objects， the manager attribute， is removed and then it needs to decide which of theother session-scoped attributes to remove.
How can this goal be accomplished？（）