现有: 3. import java.util.*; 4. class ForInTest { 5. static List list = new ArrayList(); 6. 7. public static void main(String [] args) { 8. list.add("a"); list.add("b"); list.add("c"); 9. //insert code here 10. System.out.print(o); 11. } 12. } 哪一行插入到第9行将导致输出“abc”? A. for(Object o : list) B. for(Iterator o : list) C. for(Object o : list.iterator()) D. for(Iterator o : list.iterator(); o.hasNext (); )