if引導(dǎo)條件狀語從句的時候,我們分為兩種情況,一種是真實的條件,一種是假設(shè),叫作非真實條件狀語從句
當(dāng)IF引導(dǎo)真實條件狀語從句,就要遵循我們所說的主將從現(xiàn)的原則,即主句用一般將來時,從句用一般現(xiàn)在時,比如 If all goes according to plan,the first concert will be Tuesday evening.這個就是真實的.
當(dāng)IF引導(dǎo)非真實條件狀語從句時,就要用虛擬語氣表達.
1.if + 一般過去時,與現(xiàn)在事實相反,if i were a bird ,i would fly out of the school.
2.if + should/could/would +do,與將來事實相反,if i would finish the job tomorrow,i will call you.
3.if + had done ,與過去事實相反,if i had asked you how to do it ,i would not make such a fool mistake.
怎么區(qū)別,就是看從句的時態(tài),在根據(jù)語境判斷.