def concat_answers(selected_options, delimiter):
    """synthesize answer string where there are multiple selected options"""
    if delimiter == ', ':
        return  ', '.join(selected_options[:-1]) + ' and ' + selected_options[-1]
    else:
        return delimiter.join(selected_options)
synthesize answer string where there are multiple selected options
instruction_pretrain/utils/read_compre_pt.py