It depends on what is meant by "must." All classes are
implicitly derived from Object; so in that sense, an inner class "must" extend Object. Of course, an inner class is not required to
explicitly extend anything (although it certainly
can), and it does not implicitly extend the enclosing class (although it can do so
explicitly). So considering the
word "must" along with the options provided, implicit extension of Object is the only interpretation that makes sense.
[ November 18, 2004: Message edited by: marc weber ]