Unit 6 A Great Young Athlete
it’s a long time since he studied english .他學英語很久了。
辨析since和for
since 用來說明動作起始時間，for用來說明動作延續時間長度。也就是說for 接一個時間段，since+時間起點(具體過去時間,如:1999; last+時間; 一段時間+ ago;一般過去時從句).
例如：
i have lived here for more than twenty years.我住在這兒二十多年了。
i have lived here since i was born. 我從出生起就住在這兒了。
注意：并非有for 作為時間狀語的句子都用現在完成時。
i worked here for more than twenty years. （我現在已不在這里工作。）
i have worked here for many years.（現在我仍在這里工作。）
注意：用句型轉換的方法，很容易排除非延續動詞在有for/since結構的完成時中的誤用。
1）（對） tom has studied russian for three years. = tom began to study russian three years ago, and is still studying it now.
2）（錯） harry has got married for six years. = harry began to get married six years ago, and is still getting married now.
顯然，第二句不對，它應改為 harry got married six years ago. 或 harry has been married for six years.