procedure TForm1.YesButtonClick(Sender: TObject);
var correct: boolean;
    ans : TAnswer;
begin
  retrieveAnswer(ans);
  // as it was the yes button the user pressed...
  correct := ans.answer;

  if correct and ans.known then   // user has got it correct!
    AnswerLabel.Caption := 'CORRECT!'
  else if ans.known then
    AnswerLabel.Caption := 'INCORRECT.'
  else
    AnswerLabel.Caption := '(NOT IMPLEMENTED YET)';
  AnswerLabel.Visible := true;
  if ans.known then
  begin
    AnswerLabel2.Caption := ans.feedback;
    AnswerLabel2.Visible := true;
  end;
  prepareForNewQn();
end;