a, if I have known it b,if i have had known itc,had i known itd,should i know it答案選c，不知道為什么

熱心網友

虛擬語氣與現在相反 從句IF + 主語+動詞過去式 主句 主語+WOULD/SHOULD+ 動詞原形與過去相反 從句 IF+主語+動詞的過去完成式 主句 主語+SHOULD+HAVE+過去分詞與將來相反 從句A 謂語用動詞典過去式 B謂語用WERE TO +動詞原形 C謂語用SHOULD+動詞原形 主句 主語+/WOULD/SHOULD+動詞原形從句如省略IF，用倒裝句式“WERE/HAD/SHOULD+主語eg。 Were I in school again ,I would work harder。 與現在事實相反原句 If I were in school…Had you been here earlier,you would have seen him。 與過去事實相反原句 If you had been here…Should there be a meeting tomorrow,I would come。 與將來相反原句If there should be a meeting…題目中這句話是對過去事實的相反，如果我已經知道了，就告訴你了If I had known it,I would have told you。省略IF，所以選C。

熱心網友

這個是省略了IF的句子還原來就是IF i had known it,I'd have told you.

熱心網友

這應該適于虛擬語氣的省略句在虛擬語氣的條件句中如果有were should had可以把這些詞提到主語前省略ifIf I had known it ...=had I known it...