现在完成时的被动语态
语法点拨
概念引入
Over time I have been changed quite a lot
Since the 1970s many new applications have been found for me
I have also been put into robots and used to make mobile phones as well as help with medical operations.
语法讲解
【高清课堂 B2U2语法：被动语态】
Ⅰ被动语态的概念
1. 英语中有两种语态：主动语态和被动语态。
2. 主动语态表示主语是动作的执行者
例如：Many people speak Chinese.
3. 被动语态表示主语是动作的承受着。
例如：上句可变为
_Chinese is spoken by many people.
为什么要用被动语态？
a) 当关注的是事情本身而不是动作的执行者，或者根本不知道动作的执行者时。如:
