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

2??????????

3?????Vx

4???????

5?????

??????????????????????2???????????????21? (??????????????? ????)????20???????????,??????????????????????«?????????»????????????????????????????????????????????????????????7????????,????????

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

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?,?,??????????????????????

????????????,??????????????????,??????????????????????????????????,??????13????????????????????????????????

????,??,????1??12???97%?

??????86??????

??????2??????1??????,?????,??25%????,??????????????????????10%?????????????????????2???3??????,?????,?,???????????????????30??????????2??????10????????????????,????3??????????????12??????25%???????????(??????????) ???:????????????