fixed : pezy#154

ch15/ex15.5.6/main.cpp

@@ -11,7 +11,9 @@
 //       class Base { ... };
 //      (a) class Derived : public Derived { ... }; //incorrect, deirve from itself
 //      (b) class Derived : private Base { ... };   //incorrect, this is a definition not a declaration
-//      (c) class Derived : public Base;            //correcct.
+//      (c) class Derived : public Base;            //incorrect, A derived class is declared like any other class. The declaration
+                                                    //contains the class name but does not include its derivation list.
+                                                    //@ reported by lafener, check #154 for detail.
 //! Exercise 15.5:
 //! Define your own version of the Bulk_quote class.
 //!