下列代码执行结果是（ ）public class Rectangle {public int width = 3;public int height = 4;public int area() { return width * height;} public static void main(String args[]) {Rectangle rectangle;rectangle.height = 5;System.out.println(rectangle.area());}}
选项：

A:15;
B:有编译错误，程序不能运行;
C:12;
D:0