求现在完成时.一般现在时.一般将来时.现在进行时的结构,基本用法

一、 一般现在时：
1.概念：经常、反复发生的动作或行为及现在的某种状况.
2.时间状语： always, usually, often, sometimes, every week (day, year, month…), once a week, on Sundays,
3.基本结构：动词 原形 （如主语为第三人称单数,动词上要加（e）S）
4.否定形式：am/is/are+not;此时态的谓语动词若为行为动词,则在其前加don't,如主语为第三人称单数,则用doesn't,同时还原行为动词.
5.一般疑问句：把be动词放于句首；用助动词do提问,如主语为第三人称单数,则用does,同时,还原行为动词.
6.例句：. It seldom snows here.
He is always ready to help others.
Action speaks louder than words.
过去完成时表示过去某个时间以前已经完成的动作,强调“过去的过去”.常以before, by+过去时间,或when, before等引导的过去时态的从句来表示,也可以通过上下文来表示.
　　【例如】
　　When I arrived at the station, he had already left.We had learned about 4000 English words by the end of last term.I waited until he had finished his homework.We were surprised at what she had done.We____our breakfast when an old man came to the door. (CET-4 1990,1)
　　A) just have had
　　B) have just had
　　C) just had
　　D) had just had
　　本题吃饭的动作在来的动作之前,考察过去完成时的用法,正确答案为D.
　　Before the first nonstop flight made in1949, it____necessary for all planes to land for refueling. (CET-4 1996, 6)
　　A) would be
　　B) has been
　　C) had been
　　D) would have been
　　本题时间状语从句为一般过去时,主句的情况是在从句之前,是“过去的过去”,因此用过去完成时,答案为C.
　　Until then, his family____from him for six month.( CET-4 1997, 1)
　　A) didn't hear
　　B) hasn't been hearing
　　C) hasn't heard
　　D) hadn't heard
　　过去完成时可以表示过去某一时间以前已经发生并继续发生的事情,本句考察的正是过去完成时的这一用法,故答案为D.


现在进行时：
1.概念：表示现阶段或说话时正在进行的动作及行为.
2.时间状语：now, at this time, these days, etc.
3.基本结构：am/is/are+doing
4.否定形式：am/is/are+not+doing.
5.一般疑问句：把be动词放于句首.
6.例句： How are you feeling today?
He is doing well in his lessons
现在完成时：
1.概念：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.
2.时间状语：recently, lately, since…for…,in the past few years, etc.
3.基本结构：have/has + done
4.否定形式：have/has + not +d one.
5.一般疑问句：have或has.
6.例句：I've written an article.
It has been raining these days.
一般将来时：
1.概念：表示将要发生的动作或存在的状态及打算、计划或准备做某事.
2.时间状语：tomorrow, next day(week, month, year…),soon, in a few minutes, by…,the day after tomorrow, etc.
3.基本结构：am/is/are/going to + do；will/shall + do.
4.否定形式：was/were + not; 在行为动词前加didn't,同时还原行为动词.
5.一般疑问句：be放于句首；will/shall提到句首.
6.例句：They are going to have a competition with us in studies.
It is going to rain.
过去完成时表示过去某个时间以前已经完成的动作,强调“过去的过去”.常以before, by+过去时间,或when, before等引导的过去时态的从句来表示,也可以通过上下文来表示. 构成had +过去分词
　　【例如】
　　When I arrived at the station, he had already left.We had learned about 4000 English words by the end of last term.I waited until he had finished his homework.We were surprised at what she had done.We____our breakfast when an old man came to the door. (CET-4 1990,1)
　　A) just have had
　　B) have just had
　　C) just had
　　D) had just had
　　本题吃饭的动作在来的动作之前,考察过去完成时的用法,正确答案为D.
　　Before the first nonstop flight made in1949, it____necessary for all planes to land for refueling. (CET-4 1996, 6)
　　A) would be
　　B) has been
　　C) had been
　　D) would have been
　　本题时间状语从句为一般过去时,主句的情况是在从句之前,是“过去的过去”,因此用过去完成时,答案为C.
　　Until then, his family____from him for six month.( CET-4 1997, 1)
　　A) didn't hear
　　B) hasn't been hearing
　　C) hasn't heard
　　D) hadn't heard
　　过去完成时可以表示过去某一时间以前已经发生并继续发生的事情,本句考察的正是过去完成时的这一用法,故答案为D.

一般现在时:经常性或习惯性的动作，常与表示频腮度的时间状语连用.every...,sometimes...,at....
一般过去时：used to/be used to。
一般将来时:be to,be going to,will。
现在进行时：be+V.ing 。
现在完成进行时：have/has+V.ing。
将来完成时:will have+V.ed。