What code, inserted at line 21, is called prior to a session being migrated to a different JVM assuming the web application…?

Given:

What code, inserted at line 21, is called prior to a session being migrated to a different JVM
assuming the web application containing MyExample is deployed in a container which supports
distributed applications?

A.
public void valueUnbound(HttpSessionEvent ev) {…}

B.
public void sessionPassivated(HttpSessionEvent ev) {…}

C.
public void sessionDidActivate(HttpSessionEvent ev) {…}

D.
public void sessionWillPassivate(HttpSessionEvent ev) {…}

Explanation: