?? ????????????????????
![](https://image.chezhanri.com/2019/0313/20190313113137480.jpg)
????:1????????:??????sn
2???????????
3???????????
4????????
5????????
6????28????????????,????????,??????????,??????????????????????????,?????????????????????????
??????????????????,????????,?????????????????????????,?????,???????????????????“????”,??????(?? ? ???????????? ?????????????????)
????????:??????????