下列程序运行结果是.interface InterfaceA{String s="good ";void f();}abstract class ClassA{abstract void g();}class ClassB extends ClassA implements InterfaceA{void g(){System.out.print(s);}public void f(){System.out.print(" "+s);}}public class E {public static void main(String[] args) {ClassA a=new ClassB();InterfaceA b=new ClassB();a.g();b.f();}}
选项：

A:编译正确，但无运行结果;
B:编译错误：InterfaceA b=new ClassB();;
C:good good;
D:以上都不对