[問題]關於時態

[gardenwall ()]

1.If you worked hard,you would gain a lot of money.

2.If you had worked hard yesterday,you would have gain a lot of money.


我想請問

前例1與例2的 would 和 would have是出現在假設語句中
可是常常在閱讀文章的時候
wuold/could/would have/could have
這幾個詞的出現
有時候往往並不伴隨著if的假設句法
而且文章的脈絡也不表示這是個時態處於過去的句子

以would為例:

3.Criminals can do it a lot easier than most people could imagine.

4.I don'y think many people would like to sit for such a long time in
the theaters.My bum would go into a coma.

例3與例4 .. 嗯!以前學過may/might/could/would這一類的詞
可表"較為禮貌的語氣"或"不太確定的語氣"
可是去問外國老師的時候
關於這樣的詞,解釋為"較為禮貌的語氣"或"不太確定的語氣"
好像是東方人才會這樣作解
西方人對於would/could這些字  本身就有其字義的解釋
請問有人知道像這種沒伴隨 if , 又看不出是過去時態
would與could的使用,在什麼狀態下才不會使用錯誤或正確使用呢?

以could have為例:

5.He is so handsome and such a good actor that he really
could have been a typical blockbuster star.
(例5.出自地球村生活美語11月份一篇關於強尼戴普的文章)

would have/could have  這一類詞的使用
若不伴隨if假設句,它該做什麼時態下解釋呢?
還當作"與過去事實相反"解釋嗎?

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推 johnny739:既然這樣問外國老師不是更清楚...
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