請問一個英文文法問題

Question

請問:
they are the ones who assert that a better bridge could have been built
"had" we had their assistance. 在這個句子中為什麼會多一個"had", 這是倒裝句嗎?可以解釋一下句子結構嗎?

謝謝您!

Answer 1

你可以把這句拆成:
They are the ones who assert something.
That something is: a better bridge could have been built had we had
their assistance.後面這句是假設語法. 這裡 had...had也可以寫成
if we had had their assistance. 因為是跟過去相反的假設語氣, 所以
時態要在往前推一個時間點, 也就是用過去完成式來表達. 與過去相反的假設語氣 If + S + had p.p....., S + would/could/might/ have +pp. 或是去掉 If, 直接把 Had放句首即可.

Answer 2

這是與過去事實相反假設語氣的倒裝用法："主詞 + could/would/might have P.P, if 主詞 had P.P."= "主詞 could/would/might have P.P, had 主詞 P.P." (P.P.就是過去分詞)