The following Java class definition compiles, but all its methods are instance methods:
public class Test
   private void method1(int a)
   {  System.out.println(a + x);

   public void method2(int a)
   {  System.out.println(a + y);

   public void method3()
   {  method4(new Test());

   public void method4(Test aTest)
   {  aTest.method1(17);

   private int x = 3;
   private static int y = 10;
Some of the methods can, in fact, be class methods (static). Which ones?

(a) method1.
(b) method2.
(c) method3.
(d) method4.

Select all correct answers.