Example

class ClassA {

private:int a;
private:char x;

public: ClassA () {
x='c';
}

private: class ClassB {

};


};


Solution
In the example class "ClassB" does not have any member. So, it is redundant

class ClassA {

private:int a;
private:char x;

public: ClassA () {
x='c';
}

};