What is the effect of attempting to compile and run this Java program that consists of two class definitions in separate files: 
public class One
{
   public Two get()
   {  return two;
   }

   public void set(Two theTwo)
   {  two = theTwo;
   }

   private Two two;
}

public class Two
{
   public One get()
   {  return one;
   }

   public void set(One theOne)
   {  one = theOne;
   }

   private One one;

   public static void main(String[] args)
   {  One o1 = new One();
      Two o2 = new Two();
      o1.set(o2);
      o2.set(o1);
      if (o1.get().get() == o1)
      {  System.out.println("Yes");
      }
   }
}
(a) The program compiles but, when run, gives a null pointer exception.
(b) It doesn't compile.
(c) It compiles and, when run, displays Yes.
(d) It compiles and, when run, displays nothing.

Select the most appropriate answer.