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

2????????????

3????????

4??????vx

5?????????

??12????????????18??????????????????????????????????????? ????????????????????????18?,??????????????

12?????????18?????????????????????,??????????(?)?????????????????(??????)??????????????????? ??

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

?????????????????????,?,????,?“?????????”????“????”,?,??????????,????????,????(????)

???????:????