????:1??????????????:?????

2?????

3???????????????

4????????

5???????????

?????1????8??????????????? ????????(CBC)??????(BBC)????,??1????7???,??????,???????????????“?”?????????

???:??

???,???X??:“???????????????????????????,??”

???7????,?????????????????????,???“???????????”?????

??????????,???,??“??”????????????????,???????????

??:????