虛擬語氣中的含蓄條件句問題
這是百科里的內(nèi)容：
非真實(shí)條件句中的條件從句有時(shí)不表達(dá)出來,只暗含在副詞、介詞短語、上下文或其他方式表示出來,這種句子叫做含蓄條件句,在多數(shù)情況下,條件會(huì)暗含在短語中,如without…,but for…等
eg：
1：But for his help,we would be working now.
要不是他的幫助,我們還會(huì)在工作呢.
2：Without your instruction,I would not have made such great progress.
要是沒有你的指導(dǎo),我不會(huì)取得如此大的進(jìn)步.
3：We didn't know his telephone number,otherwise we would have telephoned him.
我們不知道他的電話號(hào)碼,否則我們就會(huì)給他打電話.
請(qǐng)問各位大蝦,為什么第1句中用would ,而第二、三句卻用would have呢?有規(guī)定but for與without引領(lǐng)的含蓄條件句中這些的不同嗎?請(qǐng)?jiān)敿?xì)回答,