class Alpha { void m1() {} } 2. class Beta extends Alpha { void m2() { } } 3. class Gamma extends Beta { } 4. 5. class GreekTest { 6. public static void main(String [] args) { 7. a Alpha [] a = {new Alpha(), new Beta(), new Gamma() }; 8. for(Alpha a2 : a) { 9. a2.m1(); 10. if (a2 instanceof Beta || a2 instanceof Gamma) 11. //insert code here 12. } 13. } 14. } 哪一行代码插入到第11行,将编译但是会在运行时产生异常?()