牛津實用英語語法:154 needn't，could和should+完成式

　　A neednt+完成式常常和could+完成式結合使用。這種用法最好通過例句來說明：

　　I wanted a copy of the letter，so I typed it twice.

　　You neednt have typed it twice.You could have used a carbon.

　　我需要那封信的副本，所以我打了兩遍字。

　　你沒必要打兩遍。你當時本可以用復寫紙打。

　　I walked up six flights of stairs.

　　You neednt have walked up;you could have taken the lift.

　　我爬了六層樓梯。

　　你沒必要走著上去;你本來可以乘電梯的。

　　She stood in a queue to get an Underground ticket.

　　But she neednt have stood in a queue.She could have got a ticket from the machine.

　　她排隊買一張地鐵車票。

　　可她本來不需要排隊。她本可以在售票機那兒買票。

　　B neednt have和 should have的比較

　　should或ought to在以上A的例句中都可以代替need或could：

　　She shouldnt have stood in a queue.She should have got tickets from the machine.

　　她本來就不該去排隊。她應當在售票機那兒買票。

　　但這里存在著含義上的差別：

　　She shouldnt have stood in a queue.

　　她本來就不該去排隊。(她排隊是錯誤的或愚蠢的。)

　　She neednt have stood in a queue.

　　她本不必去排隊。(這樣做是不必要的，但她卻排了隊。)

　　shouldnt have(done)有批評之意。

　　neednt have(done)不含有批評之意。

　　A neednt+完成式常常和could+完成式結合使用。這種用法最好通過例句來說明：

　　I wanted a copy of the letter，so I typed it twice.

　　You neednt have typed it twice.You could have used a carbon.

　　我需要那封信的副本，所以我打了兩遍字。

　　你沒必要打兩遍。你當時本可以用復寫紙打。

　　I walked up six flights of stairs.

　　You neednt have walked up;you could have taken the lift.

　　我爬了六層樓梯。

　　你沒必要走著上去;你本來可以乘電梯的。

　　She stood in a queue to get an Underground ticket.

　　But she neednt have stood in a queue.She could have got a ticket from the machine.

　　她排隊買一張地鐵車票。

　　可她本來不需要排隊。她本可以在售票機那兒買票。

　　B neednt have和 should have的比較

　　should或ought to在以上A的例句中都可以代替need或could：

　　She shouldnt have stood in a queue.She should have got tickets from the machine.

　　她本來就不該去排隊。她應當在售票機那兒買票。

　　但這里存在著含義上的差別：

　　She shouldnt have stood in a queue.

　　她本來就不該去排隊。(她排隊是錯誤的或愚蠢的。)

　　She neednt have stood in a queue.

　　她本不必去排隊。(這樣做是不必要的，但她卻排了隊。)

　　shouldnt have(done)有批評之意。

　　neednt have(done)不含有批評之意。