public function questions(quiz_attempt $attemptobj, $reviewing, $slots, $page, $showall,
                              mod_quiz_display_options $displayoptions) {
        $output = '';
        foreach ($slots as $slot) {
            $output .= $attemptobj->render_question($slot, $reviewing, $this,
                    $attemptobj->review_url($slot, $page, $showall));
        }
        return $output;
    }