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

2??????

3???kb???

4???500?4????????

5????????

???????????????1??????????????????30? ????(NBC)30??,??30?????29?,????????????,??“???”??????

?1??29??,????????,????????1?30????????????????????????? ?????????????????? ????????

??,??????????????????????60??4?????????????????????????,?????3?????????????

????30?????,??3?,??????300????????????,????????????,????

NBC??????????????????,??,????

????:???