请看如下代码 ：

class Person {
    private int a; 
    public int change(int m){
        return m;
    } 
} 
public class Teacher extends Person {
    public int b; 
    public static void main(String arg[]) {
        Person p = new Person(); 
        Teacher t = new Teacher(); 
        int i; 
        // point x 
    }
}

下面哪些放在 //point x  行是正确的？ (     )