Tales of the unexplained

m2u1 grammar and usage
present perfect tense & present perfect continuous tense
一、 現(xiàn)在完成時(shí)
1、 構(gòu)成 have/has done
2、用法
i表示過(guò)去發(fā)生的事對(duì)現(xiàn)在具有影響。
1） justin has disappeared, so kelly is very sad.
2） the boy is happy. he has caught a bird.
ii表示過(guò)去開(kāi)始的動(dòng)作一直延續(xù)到現(xiàn)在或者還將持續(xù)下去。
1）i have not seen justin since last friday night.
2) daniel has lived in beijing since he came to china.
iii表示動(dòng)作的確切時(shí)間不明確或不重要。此時(shí)下列詞匯經(jīng)常和現(xiàn)在完成時(shí)連用：already, ever, never, for, just, lately/ recently, since, yet。
1） the boy has already come home.
2） i haven’t heard anything from him yet.
其中，for + 一段時(shí)間，since + 某個(gè)時(shí)間點(diǎn)。
e.g. we haven’t seen him for two days.   we haven’t seen him since last monday.
iv表示到現(xiàn)在為止的一段時(shí)間內(nèi)重復(fù)的動(dòng)作。
1） some villagers say that they have seen ufos many times.
2） i have advised him to give up smoking many times, but he just won’t listen to me.
v 現(xiàn)在完成時(shí)還可用于下列句型中：
this/it is the best/ finest/ most interesting … + that- clause,
this/it is the first/ second… time + that- clause, that 從句中的謂語(yǔ)動(dòng)詞一般用現(xiàn)在完成時(shí)。
it is/ has been a period of time since + 一般過(guò)去時(shí)
1） this is the best book that i have read.
2） it is the first time that i have seen the film.
3） it is/ has been a long time since i came to wuxi.
3、注意
1）現(xiàn)在完成時(shí)不和明確的表示時(shí)間的詞連用，如yesterday, last week, in 1976等。
2）表示短暫意義的動(dòng)詞，如begin, leave, arrive, return, stop, open, go, come, die等，不能與表示一段時(shí)間的狀語(yǔ)連用。
* read the following sentences and say t or f .
(1) he has come to beijing since last year.  f
(2) he has been here for three years.      t
(3) he has joined the army for three years     f
(4) he has been a solider for 3 years.      t
(5) it is 3 years since he joined the army.       t
(6) he has joined the army.    t
二、 現(xiàn)在完成進(jìn)行時(shí)
1、 構(gòu)成 have/has been doing
e.g. i haven’t been sleeping well since i returned home.
2、用法
表示動(dòng)作從過(guò)去開(kāi)始一直延續(xù)到現(xiàn)在，可能剛剛停止，也可能仍然在進(jìn)行。
1）-- sorry, i’m late. have you been waiting long?
   -- yes. i have been waiting (wait) for an hour.
2) she is very tired. she has been working (work) all morning.
3) the man started working in the field half an hour ago. he is still working now.
   the man has been working (work) in the field for half an hour.