A Java program consists of the following two class definitions in separate files: 
public class One
{
   public int getX()
   {  return x;
   }

   public boolean isEqualTo(One theOne)
   {  return this.x == theOne.x;
   }

   private int x = 24;
}

public class Two
{
   public int getX()
   {  return x;
   }

   private int x = 24;
}
In a main method, we create some objects as follows: 
One o1 = new One();
Two o2 = new Two();
One o3 = new One();
One o4 = o1;
In the light of this, which of the following evaluate to true?

(a) o1 == o3
(b) o4 == o1
(c) o4.isEqualTo(o1)
(d) o2.getX() == o1.getX()

Select all correct answers.