请教people的用法和一道语法题。

gouzizi

people可以加s吗？表什么意思的时候可以加呢？

Copper was the first (metal used) bu humans and is second (only) to iron (into) its utility through (the ages)

答案是C，应该改成什么呢？D是什么意思？.望指教。

[此贴子已经被作者于2004-11-22 8:31:23编辑过]

gouzizi

哦，这就去查字典。

gouzizi

C为什么要改成in 啊？