Had i known that you wanted to read it,i would have returned it immediately本人语法巨差,请问,怎么理解这个句式?希望好心人再提供几个类似的例子的应用...

If I had known that,I could have helped you.had和known怎么都是过去式,have在这里是什么意思,为什么它不用过去式 I wish I had known earlier that you could have acaree ,even if you are not top of the class . 英语一句话的理解问题 if you'd said that befor i'd have knownif you'd said that befor i'd have known 两个是不是、都是had 英语语法题目,I ( ) that you were in Shanghai last month,otherwise I ( ) you.A:had not known; would have visitB:had not known; would visitC:did not know; would have visitedD; did not know; would visit I Don't You want that.You known't me! I have just known that you don't love me. have had done与had have done区别——，I'd have told you.A.If I would have known B.If I had have known C.Had I known D.Should I know I known you would want to known that这里为什么 要加would If I_____that erlier,I wouldn't have made that mistake.A.know B.had known C.have known D.knew 3Q ..I never had to say goodbye You must have known I wouldn ' t stay 翻译：how i wish i had known you were there,too y esterday!时态有点不理解. 英语翻译I had not known him for 20 years without learning that he always . 英语翻译I had not known you a month before I felt that you were the last man in the world whom I could ever be prevailed on to marry. 英语翻译Today we buried our 20-year-old son,Jim.He was killed in a motorcycle accident on Friday night.How I wish 1 had Known when I talked to him last that it would be the last time:If I had only known 1 would have said “Jim,I love you and I 1,____ ,I would have phoned you ,a,if I knew it b,had I known it c,if I know it d,did I know it.2 ,it was because of bad weather_____ the football match had to be put off.a,so b,so that c why d,that 3,scarcely____ the room ___ the phone rang.a,I had 求3.倒装、省略、强调结构相关?倒装、省略、强调结构练习21.Here _______ now.A.come David B.David comes C.David came D.comes David22.______ that you were ill,I would have come home earlier.A.I had known B.If I know C.Had I known (1/2)I wish I had known that Ann ___ill .I would have gone to see her . 英语：1.I would have phoned you ,if I ___ time.( )A.had had B.have had C.had2.If I __ her tomorrow,I would pass your note to her.( )A.see B.shall see C.saw3.__,I'd have told you.( )A.If I would have known it B.If I had known it C.Had I known it4.T