Which among the following is correct for the following code? class A { public : class B { public : B(int i): data(i) { } int data; } }; class C: public A { class D:public A::B{ }; };

• A. Multi-level inheritance is used, with nested classes
• B. Multiple inheritance is used, with nested classes
• C. Single level inheritance is used, with enclosing classes
• D. Single level inheritance is used, with both enclosing and nested classes