protected function write_multichoice(array $multichoices, $oldquestiontextformat, $questionid) {
        global $CFG;

        // The grouped array is supposed to have just one element - let us use foreach anyway
        // just to be sure we do not loose anything.
        foreach ($multichoices as $multichoice) {
            // Append an artificial 'id' attribute (is not included in moodle.xml).
            $multichoice['id'] = $this->converter->get_nextid();

            // Replay the upgrade step 2009021801.
            $multichoice['correctfeedbackformat']               = 0;
            $multichoice['partiallycorrectfeedbackformat']      = 0;
            $multichoice['incorrectfeedbackformat']             = 0;

            if ($CFG->texteditors !== 'textarea' and $oldquestiontextformat == FORMAT_MOODLE) {
                $multichoice['correctfeedback']                 = text_to_html($multichoice['correctfeedback'], false, false, true);
                $multichoice['correctfeedbackformat']           = FORMAT_HTML;
                $multichoice['partiallycorrectfeedback']        = text_to_html($multichoice['partiallycorrectfeedback'], false, false, true);
                $multichoice['partiallycorrectfeedbackformat']  = FORMAT_HTML;
                $multichoice['incorrectfeedback']               = text_to_html($multichoice['incorrectfeedback'], false, false, true);
                $multichoice['incorrectfeedbackformat']         = FORMAT_HTML;
            } else {
                $multichoice['correctfeedbackformat']           = $oldquestiontextformat;
                $multichoice['partiallycorrectfeedbackformat']  = $oldquestiontextformat;
                $multichoice['incorrectfeedbackformat']         = $oldquestiontextformat;
            }

            $multichoice['correctfeedback'] = $this->migrate_files(
                    $multichoice['correctfeedback'], 'question', 'correctfeedback', $questionid);
            $multichoice['partiallycorrectfeedback'] = $this->migrate_files(
                    $multichoice['partiallycorrectfeedback'], 'question', 'partiallycorrectfeedback', $questionid);
            $multichoice['incorrectfeedback'] = $this->migrate_files(
                    $multichoice['incorrectfeedback'], 'question', 'incorrectfeedback', $questionid);

            $this->write_xml('multichoice', $multichoice, array('/multichoice/id'));
        }
    }