Which of the following Java statements will compile and execute without error? : Questions « Type Casting « SCJP

1. SCJP
2. Type Casting
3. Questions

import java.util.Observable;
import java.util.Observer;

class ApBase implements Runnable {
  public void run() {
  }
}

class ApDerived extends ApBase implements Observer {

  public void update(Observable o, Object arg) {
    
  }

}

public class MainClass {
  public static void main(String[] argv) {
    ApBase aBase = new ApBase();
    ApDerived aDer = new ApDerived();

  }
}
    


A.      Runnable rn = aDer ;
B.      Runnable rn2 = (Runnable) aBase ;
C.      Observer ob = aBase ;
D.      Observer ob2 = (Observer) aBase ;