What Mistake Prevents the Following Class Declaration from Functioning Properly

Multiple Choice

What mistake prevents the following class declaration from functioning properly as an abstract class? class Shape
{
Public:
Virtual double print() const;
Double area() const {return base * height;}
Private:
Double base;
Double height;
};

A) There are no pure virtual functions.
B) There is a non-virtual function.
C) private variables are being accessed by a public function.
D) Nothing, it functions fine as an abstract class.