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();}}

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