Which of the following Java classes is an abstract class?

Consider the Java program below. Choose an INVALID statement than cannot be added in the place of "// A line to be added" in the main method.

class testing {
    public final void m1() {
        System.out.println("Hey!");
    }
    public static void m2() {
        System.out.println("Salam sejahtera");
    }
}
public class Quiz2Q9 extends testing {
    public static void main(String[] args) {
        // A line to be added
    }

Which of the following statements about Java language is FALSE?

If class A inherits class B then class A is called the ___________.

Suppose you have two classes called Flight and Passenger. What is the best relationship you can create between the two classes?

Which line indicate AUTOUNBOXING in the code snippet below?

ArrayList<Double> grades = new ArrayList<Double>();
grades.add(3.2);  // Line 1
grades.add(2.7);  // Line 2
double sum = 0.0; // Line 3
for (int i=0; i < grades.size(); i++) {
    sum += grades.get(i);  // Line  4
    System.out.println("Sum = " + sum);
}

What will be the output of the program below?

import java.util.ArrayList;
public class Quiz2Q2 {
    public static void main(String[] args) throws Exception {
        ArrayList<Integer> arr = new ArrayList<>();  // 1
        arr.add(100);  // 2
        System.out.println(arr.get(arr.size()));  // 3
    }
}