UNIT THREE 一：The Key Teaching Points . 1 现在完成时（ Present Perfect Tense ） 2 和现在完成时相关的副词 3 讨论发展趋势-名词,动词,修饰 语(形容词或副词)等. 4 连接词but和so. 5 描述习惯.二：Grammar explained 现在完成时1. 现在完成时的构成：助动词 have ( has ) + 过去分词 （ 第三人称 单数用 has , 其他均用have 。）1） 现在完成时的肯定句： 主语（ 第一、二人称单、复数，第三 人称复数 ）+ have + 过去分词 主语（ 第三人称单数 ）+ has + 过去分 词 例：We have lived in Beijing .2） 现在完成时的否定句： 主语 + have ( has ) + not + 过去分词 He hasnt been to Beijing since then . 从那时起，他就再也没来过北京。 3） 现在完成时的疑问句： 一般疑问句：Have ( has ) + 主语 + 过去分词 ？ Have you finished the work ? 你已 经做完这项工作了吗 ？ Yes , I have . 是的，我已经做完了。 No , I havent . 不，我还没有做完。 特殊疑问句：特殊疑问词 + have ( has ) + 主语 + 过去分词 ？ How many times have you been to the Great Wall ? 你去过长城几次？ 动词的过去分词的三种用法： 构成： 规则动词的过去分词与其过去 式相同，即在动词原形后加 ed 或 d 构成，如动词以 y 结尾，变 y 为 i , 再加 ed 。例如： 动词原形 过去式 过去分词 work worked worked arrive arrived arrived study studied studied stop stopped stopped 不规则动词的过去分词有其特殊形式 。例如： 动词原形 过去式 过去分词 do did done see saw seen lose lost lost find found found go went gone buy bought bought find found found用法： 构成现在（ 过去 ）完成时： have ( has ) + 过去分词；He has written the letter . 他写完这 封信了。 被动语态：be + 过去分词；He was looked after . 他受到照顾。 用于形容词；This is a broken chair . 这是一张坏 的椅子。2现在完成时的用法： 1）结束、结果； 表示一个过去发生并结束的动作对现在 产生的结果和影响。 a. 表示开始于过去的动作刚刚结束。常 和just , now , already , yet , not yet 等连用。 Li Ming has just turned off the light . 李明刚刚把灯关上。 I have finished my homework now . 现在我已经做完作业了。b. 表示过去动作的结果，现在仍残留着 。一般不用时间状语： I have lost my pen . 我把笔丢了。 She has become a teacher . 她已经当了 老师。 2). 继续； I have known him for ten years . 我认识 他十年了。 表示过去已经开始，持续到现在，而且 还能继续下去的动作或状态。 往往和表示一段时间的状语连用。如： today , this week ( month ) , lately , recently , these days , in the past few days , during the last two weeks , since , since yesterday , since 2 days ago , since 1991 , for a long time , for a month , so far , up to now , till ( until ) now 等。 He has lived here for 30 years . 他住在这儿三十年了。（ 现在还住在这 儿 ）Theyve known each other since childhood . 他们从小彼此相识。（ 现在还继续往来 ） How long have you studied English ? 你学英语多久了？ （ 现在仍在学 ）3) 经验, 经历； He has never been ill in his life . 他一生 中从未生过病。表示从过去到现在之间曾经经历的事情 。常和 often , never , ever , once , twice , three times , before , since 等连用。 I have been to the Summer Palace twice . 我曾经去过颐和园两次。 We have visited your school before . 我以 前曾去过你们学校。 讨论发展趋势 -名词,动词,修饰语(形容词或副词)等. Nouns/verbs:rise, increase,go up,decrease,decline,fall,go down Adjectives:sharp(明显的 ), slow(慢的 ), slight(微小的 ), steady(平稳的 ), significant(显著的 ), rapid(迅速的 ) Adverbs: sharply, slowly, slightly,steadily,significantly,rapidly 可以使用表示增减的动词的一般 过去时来描述过去某一时间或某一阶 段发生的变化趋势. Inflation fell from 8% in 1992 to 6% in 1995.通货膨胀从1992年的8%降到 1995年的6%. In general,unemployment has risen. 总体上看失业率在上升. 限定、修饰变化趋势的词语副 词和形容词 有些副词和形容词可以用来限定、修饰 变化趋势，可参看上面所列。 Unemployment has gone up slowly. 失 业率上升缓慢。 There has been a slight rise in population.人口一直缓慢增长。 副词一般放在动词之后，而形容词一般 放在名词之前。 与描述变化趋势连用的介词： from用来描述变化的起始点。 The average wage fell from 8 per hour in 1992 to 7 in 1995. 平均工资从1992年的每小时英镑降 到了1995年的每小时7英镑. To用来描述变化的终止点。 The temperature dropped to -8 last night.昨天夜晚温度降到零下摄氏度。 By用来描述量的变化。 The average wage fell by 1 between 1992 and 1995. 1992年到1995年间平均工资下降了1英 镑。Exercise: 1. Unemployment fell by 1.5 million last year.It fell from 4.5 million to 3 million.It has already fallen by half a million this year,to 2.5 million this month. 2. Inflation rose by 4% in ten years:it was 5% in 1991,but it rose from 6% in 1992 to 9% in 1999.In 2000,however,it fell from 9% to 7%.In 2001 it decreased further by 3% and at the end of the year it was 4%. 连接词but和so but“但是，可是，而”（表示转 折） There has been a steady rise in production,but we have not employed more staff. 生产稳步增长，但是我们没有雇用 更多员工。He is old,but he looks very young. Li Li likes violin but doesnt like piano. so“所以，因此，于是”（作为连 词常用来连接因果关系分句,一般放 在结果分句的前面,与此用法类似的 还有and so. My teacher asked me to go,so I went.There has been a steady rise in production,so we have employed more staff.生产稳步增长,因此我们雇用了更多 的员工. There has been a steady rise in production,and so we have employed more staff. 如果but或so所连接的两个分句主语 是一致的,第二个分句的主语则需用代词.The Prime Minister is very popular.The Prime Minister will win the next election. The Prime Minister is very popular,so he will win the next election. 首相很受欢迎,因此他会赢得下次选举. 1. There has been a big increase in life expectancy,so there has been a big increase in the number of retired people.2. In the last ten years the number of women in work has increased sharply,but womens average wage has not increased significantly. 3. The divorce rate has gone up,but the marriage ra