人教版八年級英語下冊《I've had this bike for three years》SectionA PPT教學課件(第3課時)，共40頁。
Objectives
To learn the usage of for and since.
To use the Grammar Focus sentences to create simple conversation.
To learn new word: hometown…
Review
Group Work
You’re having a yard sale. What would you do with the money you raise?
Grammar Focus
How long have you had that bike over there?
I’ve had it for three years.
How long has his son owned the train and railway set?
He’s owned it since his fourth birthday.
Have you ever played football?
Yes, I did when I was little, but I haven’t played for a while now.
Present Perfect Tense
表示從過去已經開始持續到現在的動作或狀態，可以和表示“從過去某一時刻延續到現在的一段時間狀語”連用，如“for+時間段”、“since+過去時間點”、“since+過去時的從句”、“since+一段時間+ago”。且for與since引導的時間狀語可以相互轉換。
e.g. My uncle has worked at this factory for ten years.
= My uncle has worked at this factory since ten year ago.
I’ve lived here since 1990．
自從1990年以來我就住在這里。
I haven’t seen him for three years.
我三年沒有看見他了。
She’s been at this school since five years ago.
自從五年前她就在這個學校。
含有for，since的現在完成時的用法歌訣: 過去的動作或狀態，一直持續到現在，for、since 把時間帶。
for 和 since 在現在完成時中的應用
for與since都能與現在完成時連用，但區別較大：
（1）for后須接“時間段”
e.g. He has studied English for five years.
他學英語5年了。
（2）since后須接“時間點”
e.g. He has studied English since 1999.
他從1999年開始學英語。
（3）二者可以轉換 for + 一段時間
= since + 一段時間 + ago
e.g. He has been here for five weeks.
= He has been here since five weeks ago.
他到這兒已經有五個星期了。
（4）since能引導時間狀語從句（主句用現在完成時，從句用一般過去時），而for則不能。
e.g. He has taught here since he came to China.
自從他來到中國就在這兒教書。
（5）現在完成時常用句型：
①It is (has been) +時間段+ since +時間狀語或從句 e.g.
It is four days since last Friday.
從上周五到現在已經四天了。
It has been two years since Jim came to Beijing.
吉姆來北京已經兩年了。
Homework
Review the Grammar Focus and tell the differences between for and since.Then make sentences with them.
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