多选题 Given this code in a method:
4. Integer[] [] la = {{1,2}, {3,4,5}};
5. Number[] na = la[1];
6. Number[] na2 = (Number[])la[0];
7. Object o = na2;
8. la[1] = (Number[])o;
9. la[0] = (Integer[])o;
What is the result? (Choose all that apply.)