Which is true?

Given the definition of Myobject and that an instance of Myobject is bound as a session attribute:
8. package com.example;
9. public class Myobject implements
10. javax.servlet.http.HttpSessionBindingListener {
11. // class body code here
12. }
Which is true?

A.
Only a single instance of Myobject may exist within a session

B.
The unbound method of the Myobject instance is called when the session to which it is bound times out

C.
The com.example.MyObject must be declared as a servlet event listener in the web application deployment descriptor

D.
The valueUnbound method of the Myobject instance is called when the session to which it is bound times out