RG9u9
When was it invented ?
Grammar
The passive voice
1.The past tense.
助动词be (was/were) +及物动词的过去分词。
Bell invented the telephone in 1876.
The telephone was invented by Bell in 1876.
陈述句 They were invented last year.
           A car wasn’t invented in 1971.
一般疑问句 Were they invented last year ?
Yes, they were. No, they weren’t
特殊疑问句  When were they invented ?
Function
Talk about the history of inventions.