Unit 9 When was it invented? Section A(1a-2c)Learning goals:Talk about the history of inventions and their uses by using the passive voice.Step 1 Preview如何理解被动语态？ 为取胜更清晰、更深刻地理解被动语态的含义，可以将主动语态和被动语态的句子结构进行比较。 主动语态： 主语+ 谓语动词 + 宾语 + 其他成分 被动语态： 主语+ be +过去分词 + by +宾语 +其他成分 如： Many people speak English.被动语态 English is spoken by many people.一专项训练1. The bridge _ （build） by the farmers themselves in 1982.2. All the books will _（send） to the c
