About Question com.enthuware.ets.scjp.v6.2.580 :

[ETS User]

Here is as well looks like something missing:

The method in C needs to call a method in a superclass two levels up. The super.super.perform_work( ) strategy will not work, since super is a keyword, not an attribute.
). There is no way to go more than one level up for methods.

[admin]

This has now been fixed.

thank you for your feedback!