This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
The method needs to return a Carpet of V, or a Carpet of something that inherits V; What is V will be decided when an instance of Carpet is instantiated. And it is not clear if B or C fulfills the IS-A V test.