导学：一般现在时表示主语经常性和习惯性的动作或存在的状态，也表示说话者的能力及自然现象。现在完成时则表示过去发生或已经完成的动作对现在造成的影响或结果，或从过去已经开始，持续到现在的动作或状态。为了更好的区分它们，我们来看下面的句子。
（1)I come from Shanghai．(上海人)I have come from Shanghai．(从上海来)(2)You read very well．(强调能力)You've read very well．(强调一次刚完成的动作)(3) I forget．(一时想不起来了)I have forgotten．(仍没想起来，可能已回忆起来了)(4) The book is written in simple English．(表状态)The book has been written in simple English．(表动态，已用英语写成)(5) Every time I see him，he's been reading．(两个动作不可能同时进行)．Every time l have seen him，he's been reading．(强调两个动作同时进行)(6) He is gone．(强调状态)He has gone．(强调动作和时间)(7) He won't come till the play begins．(演出开始时)He won't come till the play has begun．(戏已开始)
（1)I come from Shanghai．(上海人)I have come from Shanghai．(从上海来)(2)You read very well．(强调能力)You've read very well．(强调一次刚完成的动作)(3) I forget．(一时想不起来了)I have forgotten．(仍没想起来，可能已回忆起来了)(4) The book is written in simple English．(表状态)The book has been written in simple English．(表动态，已用英语写成)(5) Every time I see him，he's been reading．(两个动作不可能同时进行)．Every time l have seen him，he's been reading．(强调两个动作同时进行)(6) He is gone．(强调状态)He has gone．(强调动作和时间)(7) He won't come till the play begins．(演出开始时)He won't come till the play has begun．(戏已开始)
