从石器、青铜器到铁器时代，金属的冶炼体现了人类文明的发展水平。下图表示了三种金属被人类开发利用的大致年限。之所以有先后。主要取决于（ ）
Wuchazi Bridge as an Internet﹣famous place in Chengdu． （ ）
regards
is regarded
is regarding
Molly， my dictionary is not here． Do you have ？ （ ）
it
that
one.
Life is like a horse， and you ride it it rides you． （ ）
either； or
neither； nor
both； and
The book cover has a beautiful picture is Lily's．（ ）
A．whichB．whoseC．that
﹣Labor（劳动）education is important for students' development．
﹣Yes． schools put it into practice， students will be more independent and helpful． （ ）
While
Unless
If
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