Unit 3 Language in use Look at the following sentences, paying attention to their tenses.1.He has been popular for over eighty years.2.Tintin appeared in China in the 1980s.3.Snoopy lives in his own private world.4.They look very different, but both of them have won the hearts of young people all over the world. 一般现在时，一般过去时与现在完成时的区别一般现在时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，动词上要改为第三人称单数形式） 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. 一般过去时1. 概念 : 过去某个时间里发生的动作或状态；过去习惯性、经常性的动作、行为。2. 时间状语 : ago, yesterday, the day before yesterday, last week, last (year, night, month…), in 1989, just now, at the age of 5, one day, long long ago, once upon a time, etc.3. 基本结构 : be 动词；行为动词 的过去式 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 : was 或 were 放于句首；用助动词 do 的过去式 did 提问，同时还原行为动词。6. 例句 : She often came to help us in those days. I didn't know you were so busy. 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 +done. 5. 一般疑问句 : Have...
