namespace N{

  class C {            
                       
  }                    

  public class D{

    public C M(){      // Compiler-time error message:
      return new C();  
                       // Inconsistent accessibility: 
                       // return type 'N.C' is less
                       // accessible than method 'N.D.M()'
    }

  }

}

 
 
Implicitly class C has internal visibility.
We have most likely forgotten to declare 
the visibility of C in the namespace N.