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

2????????

3???????

4????????

5???????

????????????2????16? ?,????,2?????????16???????20???17??20?????,???????????????????????????????????????????????4~6??????7~8??;?????????????????????????????????????????????????????????????7????8???

??:??

???????:

1????????????????????????,??;

2????????????????,?????????????????;

3???????????????????????????,???????????;

4??????????????,???

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