1 一般现在时一般现在时结构：do/does一般现在时的定义：表示现在发生的动作、情况、状态和特征。一般现在时的被动语态构成：is / am / are +V过分Our classroom is cleaned everyday. I am asked to study hard by my mother. Knives are used for cutting things. 2 一般过去时一般过去时结构：did(即动词-ed)一般过去时的定义：表示过去某个时间发生的动作或情况 一般过去时的被动语态构成：was / were + V过分A new shop was built last year. Dinosaur eggs were laid long long ago. 3 现在完成时结构：have+动词-ed现在完成时的定义：表示动作到现在为止已经完成或刚刚完成。 现在完成时的被动语态构成：has / have + been + V过分This book
