1. 主动语态与被动语态的转换
　　【经典例题】Many workers built this factory in 2001. This factory ___ ____ by many workers in 2001.

　　【名师精解】本题的正确答案为：was built.正确解题的关键是被动语态的构成(built――be built)和过去时态(be动词要用was，与原句的built对应)。