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 String getVar()
   {  return var;
   }

   private String var;
}

public class Two
{
   public static void main(String[] args)
   {  One obj= new One();
      System.out.println(obj.getVar());
   }
}
(a) The program compiles but, when run, displays an error message.
(b) It compiles and, when run, displays the empty string.
(c) It doesn't compile.
(d) It compiles and, when run, displays a line of spaces.
(e) None of the above.

Select the most appropriate answer.