单选题 The period during (when) people (learned to) smelt iron is (called) (the) Iron Age.
  • A. when
  • B. learned to
  • C. called
  • D. the


【正确答案】 A
【答案解析】[分析] 本题考查“介词+which”引导定语从句。when不用在介词后。改“when”为“which”。