???

?? ???? ?????
???
.?,?.?,?,??..

?
1.????? 2.??????? 3.??????? 4.???

???????B????????????X??????
??????????????????????23?50????
[?]
????? ??????????????????????????????????????????????????????????
???????????????????????????????????????????????
??????????????????95??????????????95????????????????????????????????????????????? ...

??????????????????95??????????????95?????????????????????????????????????????????
????????????????????????????????????????????????
? 1.????? 2.??????? 3.??????? 4.???
1.??? 2.???? 3.????
? 1.????? 2.?? 3.??
?? 1.???AB? 2.???ABC?? 3.??????

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

??????????????

???5??4.5g/cm3??????????

??????

??(ferrous)(non-ferrous metal)???? ?????????

??????4.5g/cm3?????(?????)

???.
???????
??3
????800???????7???????????????????????,?????????????????????????

??

1. ? ????? ?

2. ?d??????? ??? ?^???????

3.?d??? ???? ]?????^...

6C
7B
8D