??????????? ??? ??????????????? ???????? ????? ????????! ??????? ????? ?? ???????? ??????????? ????? , ???? ??????? , ??? ??????? ???????????? ??? ???????? ??????? ???????? ????????? : du l?ch ???????? ????? ???????? có ?????? n?i ngo?n m?c ?????? ???? môi tr??ng t??i ??p . ng??i ta có th? ??