Unit3 The Computer and the Information Age-grammar教案
3》警示 进行时还常用在语境中，表示语气的委婉。如： ---what are you going to do? ---i'm hoping to invite you to dinner. 5.完成时。 1》概念 本时态是表示某动作或某过程在一定时间内处于完成的状态。 2》理解 完成时包括现在完成时和过去完成时态。构成分别为have<has> done/had done. <一>现在完成时。动作在过去发生，持续到现在已经完成，或者是继续持续下去。 <1> 已经完成的用法。其表明某动作或过程发生在说话前某个不明确的过去时刻，到目前一完成，并对目前造成影响。如：he has not been to shanghai/have you finished reading the story ? 本用法常和不确定时间状语连用。如：already/yet/before/recently/lately/just...等 i have seen him before we haven't been there lately 也可以和表示频度的时间状语用在一起。如：ever/never/once---等。 i have never been to hongkong. have you ever visited the great wall ? <2> 未完成的用法。本用法表示某动作或状态开始于过去某个时刻一直延续到现在，而且还要继续下去，在某种情况下也可能刚刚结束。常和 since/for/时间状语连用。如： he has been in the army for 3 years. he has lived in the building since he came here. 3》警示：如果不过since 引导的从句中的动词是延续性的，一般认为，语意上也表明动作或状态的结束。如： i haven't heard from him since he lived there. 从他离开那儿以来，我一直未收到他的消息。 he has written to me frequently since i was ill. 从我病愈以来，他常给我写信。 如果since引导的从句中的谓语动词用了现在完成时，那么表示的动作或状态就不表示完结。如： i haven't heard from him since he has lived there . 从我住在那里以来，我一直未收到他的来信。 he has written to me frequently since i have been ill. 从我生病以来，他常给我写信。 <二>过去完成时。本时态表示的是动作在过去的过去发生。它也分为“已完成用法”和“未完成用法”。 1>已完成用法。表示，当一个动作发生或结束时，在它之前的另一动作已经完成。这种用法既用于动作动词，也用于状态动词。如： when we arrived the cinema,the tickets have been sold out. tom flew home,but his father had already died.
