Which is a valid abstract class?

Given the code fragment:

Which code fragment, inserted at line n1, pints The Top element: 30?

Given the code fragment:

What is the result?

Given:

Which code fragment should you use at line n1 to instantiate the dvd object successfully?

Given:
public class TestField {
int x;
int y;
public void doStuff(int x, int y) {
this.x = x;
y =this.y;
}
public void display() {
System.out.print(x + " " + y + " : ");
}
public static void main(String[] args) {
TestField m1 = new TestField();
m1.x = 100;
m1.y = 200;
TestField m2 = new TestField();
m2.doStuff(m1.x, m1.y);
m1.display();
m2.display();
}
}
What is the result?