7.现在完成时的"未完成用法"
现在完成时的"未完成用法"指的是动作开始于过去某一时刻，一直延续到现在，或可能还要继续下去。
例如：
He has lived here since 1978.自从1978年以来，他一直住在这儿。
（动作起始于1978年，一直住到现在，可能还要继续住下去。）
I have been in the army for more than 5 years.我在部队已经呆了五年多了。
（动作开始于5年前，一直延续至今，有可能还要继续下去。）
此种用法的句中常需一个表示一段时间的状语（由since或for引导），或表示与现在时刻相连的时间状语（如：up to now，so far）等。
例如：
I have heard nothing from him up to now.到目前为止我没有他的任何消息。
注意：现在完成时的未完成用法只适用于延续性动词，不可用于终止性动词，即瞬间完成或延续时间很短的动词。
如：come，go，arrive，leave，join，become，die等。
8.一段时间+has passed+since从句
主语＋have / has been＋since短语
例如：He has been in the League for three years.
或It is three years since he joined the League. 他入团已三年了　　
9. 现在完成时常和短语 "up to now /till now","so far" （意思是从过去某一确定的时间一直延续到现在)连用。　　
Up to/till now he's read many story books. 至今他已读过好多故事书。
I've been to New York three times so far. 至今我已到纽约去过三次。
has gone (to),has been (to),has been (in) 的区别
has gone to：去了没回
has been to ：去过
has been in：呆了很久

考点名称：状语从句

• 状语从句：
  指句子用作状语时，起副词作用的句子。它可以修饰谓语、非谓语动词、定语、状语或整个句子。
  根据其作用可分为时间、地点、原因、条件、目的、结果、让步、方式和比较等从句。
  状语从句一般由连词(从属连词)引导，也可以由词组引起。
  从句位于句首或句中时通常用逗号与主句隔开，位于句尾时可以不用逗号隔开。

• 状语从句分类:
  1、时间状语从句
  常用引导词：
  when, as, while, as soon as, while, before, after, since , till, until
  特殊引导词：
  the minute, the moment, the second, every time, the day,the instant, immediately , directly, no sooner … than, hardly …when, scarcely … when
  I didn't realize how special my mother was until I became an adult.
  While John was watching TV, his wife was cooking.
  The children ran away from the orchard(果园) the moment they saw the guard.
  No sooner had I arrived home than it began to rain.
  Every time I listen to your advice, I get into trouble.
  
  2、地点状语从句
  常用引导词：
  where
  特殊引导词：
  wherever, anywhere, everywhere
  Generally, air will be heavily polluted where there are factories.
  Wherever you go, you should work hard.
  
  3、原因状语从句
  常用引导词：
  because, since, as, for
  特殊引导词：
  seeing that, now that, in that, considering that, given that, considering that, as much as, so much as
  My friends dislike me because I'm handsome and successful.
  Now that everybody has come, let's begin our conference.
  The higher income tax is harmful in that it may discourage people from trying to earn more.
  Considering that he is no more than 12 years old, his height of 1.80 m is quite remarkable.
  
  4、目的状语从句
  常用引导词：
  so that, in order that
  特殊引导词：
  lest, in case, for fear that,in the hope that, for the purpose that, to the end that
  The boss asked the secretary to hurry up with the letters so that he could sign them.
  The teacher raised his voice on purpose that the students in the back could hear more clearly.
  
  5、结果状语从句
  常用引导词：
  so that, so… that, such … that,
  特殊引导词：
  such that, to the degree that, to the extent that, to such a degree that,
  He got up so early that he caught the first bus.
  It's such a good chance that we must not miss it.
  To such an degree was he excited that he couldn't sleep last night.
  
  6、条件状语从句
  常用引导词：
  if, unless,
  特殊引导词：
  as/so long as, only if, providing/provided that, suppose that, in case that, on condition that
  We'll start our project if the president agrees.
  You will certainly succeed so long as you keep on trying.
  Provided that there is no opposition, we shall hold the meeting here.
  
  7、让步状语从句
  常用引导词：
  though, although, even if, even though
  特殊引导词：
  as(用在让步状语从句中必须要倒装),while ( 一般用在句首 ),no matter …, in spite of the fact that, while, whatever, whoever, wherever, whenever, however, whichever
  Much as I respect him, I can't agree to his proposal.
  尽管我很尊敬他, 我却不同意他的建议。
  The old man always enjoys swimming even though the weather is rough.
  No matter how hard he tried, she could not change her mind.
  He won't listen whatever you may say.
  
  8、比较状语从句
  常用引导词：
  as(同级比较), than(不同程度的比较)
  特殊引导词：
  the more … the more … ; just as …, so…; A is to B what /as X is to Y; no … more than; not A so much as B
  She is as bad-tempered as her mother.
  The house is three times as big as ours.
  The more you exercise, the healthier you will be.
  Food is to men what oil is to machine. 食物之于人,犹如油之于机器。
  
  9、方式状语从句
  常用引导词：
  as, as if, how
  特殊引导词：
  the way
  When in Rome, do as the Roman do.
  She behaved as if she were the boss.
  Sometimes we teach our children the way our parents have taught us.

• 状语从句用法:
  时间状语从句
  (1) when引导的时间状语从句
  ①.when引导的时间状语从句，其动词既可以是延续性动作的动词，也可以是瞬间性动作的动词，而且可以表示主句的动作和从句的动作同时发生，或者从句的动作发生在主句的动作之前。如：
  when you apply for a job, you must present your credentials.
  当你申请工作时，你必须递交你的有关证件。（同时）
  when the students heard the teacher’s footsteps, they all atopped talking.
  当学生们听到老师的脚步声时，他们都停止了讲话。（从句动作发生在前）
  ② when还可表示just then（正在那时，突然）的意思，此时其所引导的从句只放在主句之后。如：
  we were about to start when it began to rain.
  我们正要动身，突然天下起雨来。
  The game had hardly/scarcely/barely begun when it started raining.
  比赛刚刚开始就下起雨来。
  (2) as引导的时间状语从句
  as引导的时间状语从句其动词的动作是延续性的，而且侧重表示主句和从句的动作并相发生：
  We were having breakfast as she was combing her hair.
  她梳头时我们在吃早饭。
  It will warm up a little bit on Sunday as the cold front passes.
  寒流一过，星期日就会有点暖意了。
  (3) while引导的时间状语从句
  while表示“在某一段时间里”或“在……期间”，其所引导的从句的动作是延续性的，并侧重表示和主句的动作同时发生。如：
  When the teacher paraphrased the text in English, the students listened attentively and took notes.
  当老师用英语解释课文时，学生们聚精会神地听并做着笔记。
  I can learn while I work.
  我可以边工作边学习。
  (4) before引导的时间状语从句
  ① before“在……之前”
  I have finished my dissertation before my supervisor went abroad.
  在我的导师出国之前，我已完成了我的学位论文。
  I’ll be back before you have left.
  你离开之前我就会回来。
  ② before“……之后才”
  It may be many years before we meet again.
  可能要过许多年我们才能再见了。
  It was three days before I came back.
  他三天后才回来。
  (5) as soon as/once/directly/the instant等引导的时间状语从句
  as soon as 是最常见的表示“一……就”的从属连词，其他连词还有once，directly，immediately，instantly，the instant (that)，the minute(that) ，the moment(that)等，它们通常都可与as soon as换用。如：
  As soon as we got home, the telephone rang.
  我们一到家，电话就响了。
  I recognized her immediately I saw her.
  我一看见她就认出她来了。
  Directly the teacher came in everyone was quiet.
  老师一进来，大家就静了下来。
  (6) hardly...when/no sooner...than引导的时间状语从句
  关联从属连词hardly/barely/scarcely...when和no sooner...than的意思是“刚……就”，它们所引导的从句中的谓语动词通常为过去完成时。如：