which enables a BroadcastReceiver callback?

Which of these is the correct code which enables a BroadcastReceiver callback?

A.
public class ReceiverSample extends BroadcastReceiver {
public void onCreate(Context context, Intent intent) {}
}

B.
public class ReceiverSample implements BroadcastReceiver{
public void onCreate(Context context, Intent intent) {}
}

C.
public class ReceiverSample extends BroadcastReceiver{
public void onReceive(Context context, Intent intent) {}
}

D.
public class ReceiverSample implements BroadcastReceiver {
public void onReceive(Context context, Intent intent) {}
}

Explanation: