A-A+
The period during (when) people (learned to) s
问题详情
The period during (when) people (learned to) smelt iron is (called) (the) Iron Age.
A．when
B．learned to
C．called
D．the请帮忙给出正确答案和分析，谢谢！
参考答案
正确答案：A
解析：本题考查“介词+which”引导定语从句。when不用在介词后。改“when”为“which”。
