One of our friends had a Java job interview a few days ago. He put "RMI" in his resume but he did mention in which project he used RMI. Unfortunately, he was asked the above question and he got stuck. As he talked me, I told me he understood RMI and just did some exercises following "Core Java II".

This friend is right now doing EJB stuff. Here is the answer I cooked up for him----
We used RMI in this EJB project extensively.
Actually, RMI is ubiquitous in EJB. In our project, all the beans communicate using
an enhanced RMI protocol, and it is called
RMI over IIOP.

The point in answering this kinds of questions is that one needs courage.
In this world, there are only a handful of
true Java experts. As you have sth you are not sure, just go ahead and talk boldly. Even
you meet true experts, they usually don't point out your mistakes.