public function display_options_adv() {
        echo \html_writer::start_div();
        echo \html_writer::empty_tag('input', array('type' => 'hidden', 'name' => 'recurse',
                                               'value' => 0, 'id' => 'recurse_off'));
        echo \html_writer::checkbox('recurse', '1', $this->recurse, get_string('includesubcategories', 'question'),
                                       array('id' => 'recurse_on', 'class' => 'searchoptions'));
        echo \html_writer::end_div() . "\n";
    }