鉛筆and小新
合乎邏輯即可。
一般情況下，主從句時態是分別由語境決定的，並不互相牽制，互相影響。賓語從句除外。
以定語從句為例，
He married a girl whose father is a billionaire.
He married a girl whose father was a billionaire.
He married a girl whose father has been a billionnaire.
三個句子都沒錯，只是表意有差別。
第一個表示他娶的女孩的父親是個億萬富翁；第二個表示女孩的父親過去是個億萬富翁，現在是不是不知道；第三個表示女孩的父親曾經是個百萬富翁，現在已經不是了。
賓語從句涉及到主從句時態的牽制問題，因為涉及到間接引語。也就是從句的動作和主句的動作時間上有聯繫，所以要考慮主從句時態的搭配。
例如，賓語從句主句是過去時態，從句應該也在過去時態的範圍內的時態。
He said his son was studying English.
他說他的兒子正在學英語。
主句一般過去時，從句過去進行時。
He said his son had passed CET-4.
他說他的兒子已經過了英語四級。
從句動作發生於主句動作之前。主句一般過去時，從句過去完成時。
英語學人
借鑑他人總結：
英語中六大從句用法總結1.主語從句1）主語從句可直接位於主語的位置，如果從句較長，謂語又較短，可用it作形式主語，而將從句放在句末。常見的句型有：*It is a fact\\a pity\\a question\\good news that...*It seems\\appears\\happened\\has turned out that...*It is clear\\important\\likely\\possible that...*It is said\\reported\\estimated\\has been proved that...It is said that comic books create a connection between people of the same generation.It seems that the performance is very useful.2)what引導的主語從句表示“...的東西時”，一般不用it作形式主語。What we lack is experience.3)what,who,when,why,whether等詞含有各自的疑問意義，但它們引導的主語從句，都用陳述語序。How the plan is to be carried out should be discussed again.I did know why I felt like crying.2.賓語從句1）賓語從句可位於及物動詞、介詞和某些形容詞後。連詞that常可省略。介詞後一般接疑問詞引導的賓語從句。in that(因為),except that(除了),but that(只是）已構成固定搭配，其他介詞後一般不接that引導的賓語從句。*I promised that I would change the situation.*All this is different from what American young people would say about friendship.*He is certain that watching so much television is not good for children.*This article is well-written except that it is a bit too long.2)賓語從句後如有賓補，要用形式賓語it來代替，而把賓語從句移至賓補之後。He has made it clear that he would not change his mind.3)在think,believe,suppose,expect等動詞後的賓語從句中，如果謂語是否定的，一般將否定詞移至主句謂語上，賓語從句則變成肯定形式。He didn't think that the money was well spent.3.表語從句表語從句出現在結構為“主語+系動詞+表語從句”的句子中。表語從句除可用that,what,when,why,whether,how等引導外，還可由because,as if(though)等引導。that常可省略。如主句主語為reason,只能用that引導表語從句，不可用because.Perhaps the most important thing to remember is that there is no one common type of life in America.The reason why so many people died there is that there were not enough food supplies.It looks as if successful international cultural communication will make the world smaller.4.同位語從句同位語從句用於對前面出現的名詞作進一步說明，一般用連詞that引導，由於先行名詞的意義不同，也可用whether,who,when,where,what,why,how等引導。常見的先行名詞有fact,idea,belief,news,hope,conclusion,evidence,suggestion,order,problem,report,decision.有時由於謂語較短，將同位語從句位於謂語之後。She finally made the decision that she would join the fashion show.I had no idea how many books I could borrow at a time.The news came that their team had won the championship.5.定語從句定語從句所修飾的先行詞可以是名詞或代詞，也可以是一個句子。定語從句通常位於先行詞之後，由關係代詞或關係副詞引導。*限制性定語從句限制性定語從句修飾先行詞，對先行詞起修飾作用，緊接先行詞之後，無逗號，若省去，原句意思不完整。引導定語從句的關係代詞有who,whom,whose,which,that等。who,whom,whose用於指人，whose有時也可指物，相當於of which；which用於指物；that既可指人也可指物，但只用於限制性定語從句中。關係代詞除了引導定語從句，替代先行詞外，還在從句中擔任主語、賓語、定語等。The computers and cables which make up the Internet are owned by people and organizations.Those who live alone or who are sick may have trouble in getting close to other people.The girl whose parents died in an accident is living with her grandmother.1)當先行詞是all,anything,everything,something,nothing等不定代詞或先行詞前有first,last,any,few,much,some,no,only以及形容詞最高級修飾時，只能用關係代詞that引導從句。That is all that I've heard from him.He's the first person that I'm going to interview this afternoon.2)關係代詞的省略在從句中作賓語的關係代詞常可省略。關係代詞緊跟介詞，作介詞賓語時不可用that，只可用which或whom引導從句，並且不可省略，但當介詞位於賓語從句句末時，作為介詞賓語的關係代詞仍可用that，也可省略。This is one of those things with which we have to put up.This is one of those things (which\\that) we have to put up with.3)引導定語從句的關係副詞有when,where,why等。關係副詞在從句中作狀語，意義上相當於一個“介詞+which”的結構。Even in comic books where(=in which) there are no words,the stories are fully expressed through the drawings.No one knows the reason why(=for which) he was so angry that day.5.定語從句*非限制性定語從句非限制性定語從句既可修飾先行詞，也可修飾整個主句，起補充說明作用，與主句之間有逗號隔開，若省去，原句意思不受影響。不可用that引導非限制性定語從句。關係詞不可省略。Every object has a gravitational pull,which is rather like magnetism.*“介詞+which\\whom\\whose”引導的定語從句“介詞+which\\whom\\whose”可引導限制性定語從句，也可引導非限制性定語從句，該結構中介詞的選擇取決於從句謂語動詞的固定搭配，或先行詞的習慣搭配。This is the computer on which he spent all his savingsIt is written by a person with whom we are all familiar.*as引導的定語從句as引導的定語從句主要用於“such...as”及“the same...as”的結構中，代替先行詞是人或物的名詞。as引導非限制性定語從句時，代替整個主句，從句可位於主句之前、之後或中間。These are not such problems as can be easily solved.(as代替先行詞problems)As is mentioned above,no single company or group can control what happens on the Internet.(as代替主語)6.狀語從句*時間狀語從句引導時間狀語從句的從屬連詞和詞組有：1）when,whenever,while,as,after,before,since,till,until,once等。We have learnt quite a lot about it since we came here.2)as soon as,hardly(scarcely)...when,no sooner...than,each(every) time,the moment,immediately(that)等。As soon as I sent an e-mail message,I received positive responses.The moment he heard the good news,he jumped with joy.*地點狀語從句引導地點狀語從句的連詞是where,wherever.Wherever she went,she took her little daughter with her.*原因、結果和目的狀語從句1）引導原因狀語從句的從屬連詞有：because,as,since,now(that),seeing that,considering that,in that等。Considering that he is a freshman,we must say he is doing well.2)引導結果狀語從句的連詞有：so...that,such...that,so that,that,so等。Mickey Mouse is so attractive that the children are reluctant to leave.3)引導目的狀語從句的連詞有：so that,in order that,for fear that,lest等，從句常使用may,might,can,could,would等情態動詞。We got up early this morning so that we could catch the first bus to the railway station.*條件和讓步狀語從句1）引導條件狀語從句的連詞和詞組有if,unless,as(so) long as,on condition that,in case,provided(providing) that,supposing等。As long as you have the right equipment,you can use a telephone line to transmit computer data.2)引導讓步狀語從句的連詞和詞組有though,although,whether,even though,even if,no matter what(when,how...),whatever(whenever,wherever,however....)等。though,even if等引導狀語從句可轉換成含有as的部分倒裝結構，具有強調意義。其結構為“形容詞（副詞、動詞、名詞）+as+主語+謂語”。No matter what you may say,I would not change my mind.Young as he is,he is quite experienced in this work.(=though he is young)Child as he is,he can speak English fluently.(=though he is a child)*方式狀語從句引導方式狀語從句的連詞有as,just as,as if,as though等。as if,as though引導的狀語從句中，謂語動詞常用虛擬語氣，表示與事實相反。The young man made the experiment just as the teacher had taught him.Everything went on as usual as if nothing had happened.
自然習英語
英語語法中，從句共分為六種，分別為：
- 主語從句
- 賓語從句
- 表語從句
- 同位語從句
- 定語從句
- 狀語從句
以上從句的定義是由該從句在複合句中所作的成分作出的，即：作主語的句子，叫主語從句; 作賓語的句子，叫賓語從句，其他類同，不一一列出。
如：Whether he will come is not known.(主語從句)
We don't know whether he will come. (賓語從句)
所有從句有幾個共同點：
第一，所有從句開頭都有一連接從句的連接詞，或者叫引導詞，它們標誌著從句的開始。其中賓語從句的連接詞that可省略，定語從句中引導詞在從句中作賓語時可省略。第二，所有從句中除了開頭的連接詞外，都要用陳述語序，也就是按“主謂賓”的順序排列詞彙。
就時態方面而言：
第三，所有自然界的客觀真理性句子作從句時，從句都要用一般現在時態，主句則根據實際情況而定。如，
That the earth moves around the sun is a fact.(主語從句，地球圍繞太陽轉，是客觀事實，用一般現在時)
第四，除去講述自然界客觀事實外，各主從句中的具體時態通常根據實際情況，也就是說話人當時的具體時間狀況，來確定。舉例說明：
如果大家對於“根據實際情況確定時態”有困難，那麼，我再用另一種思路講：把所有讀到的句子假設成“你”“現在”要說的話，①說出此話時，已經發生的動作就是過去，用一般過去時; 如果有兩個動作已經發生，那麼先發生的那個動作，就是“過去的過去”，用過去完成時，後發生的用一般過去時; 如果這兩個動作同時發生，那麼可以都用一般過去，也可以主句用一般過去，從句用過去進行時。②說出此話時，還未發生，將要發生的動作就是將來，用一般將來時，或者強調將來某具體時刻發生，就用將來進行時。③說出此話時，正在發生的動作就是進行，用現在進行時。④強調到說話的此刻已經完成的動作，就用現在完成時。⑤表示在說話的此刻正存在的一種狀態動詞，就用一般現在時。主語從句：When he returned yesterday is the important question.
Where the meeting will be held tomorrow has not been decided.
賓語從句：He was asked where he had come from before and where he was living then.
It depends on whether the mayor will agree to the proposal.
表語從句：That is why I am working hard at my lessons now.
That is how I figured it. 這就是我(過去）對它的看法。
同位語從句：Yu must live with the fact that you were beat in the match.
定語從句：He gave the best speech that I had ever listened to.
This is the best speech that I have ever listened to.
狀語從句：Because he was ill yesterday, he didn't go to school.
As soon as I received your letter, I come here at once.
第五，各從句中對時態的特殊要求。
① 有些從句受虛擬語氣的影響，句子謂語要用should +動詞原形或者其他形式。
主語從句中用虛擬語氣的句型：
It be +名詞/形容詞+主語從句 (should+動原)
It is necessary /important /a duty that we should help the old.
② 與表示建議，要求，命令意義的詞彙相關的賓語，表語，同位語從句，要用到虛擬語氣，從句謂語用should +動原形式。
His suggestion is that the factory should promote their product.
③ wish ,would rather 後面的賓語從句，要用虛擬語氣，所以從句謂語動詞時態要考慮虛擬語氣用法。
I wish/would rather I had reviewed the lesson before the text.
④ 在if 引導的條件狀語從句中，當說話人表達非真實的語義時，主從句要考慮虛擬語氣的用法。
⑤在有表示時間，條件意義的的狀語從句時，當說話人講述將要發生的事情，從句要用一般現在時態，主句用將來時態，這就是俗稱的“主將從現”。
If it rains tomorrow, I will go to plant trees.
羅敷講中高考英語
這個感覺還是按語意來較好。
1. 他昨天說她下午到這裡。
(中文有歧義的句子)
2. 他昨天說她昨天下午到這裡。
(中文意思明確)
3. 他昨天說她今天下午到這裡。
(中文意思明確)
1a. He said she would come here in the afternoon. 意思比較明確, 但不全等於中文
1b. Yesterday afternoon, he said she would come here. 意思比較明確，但不全等於中文
1c Yesterday, he said she would come here in the afternoon. 意思明確
2. He said yesterday she would come here in the afternoon. 意思明確, 同1c.
3a. He said yesterday she would come here in the afternoon. 意思不明確，與2搞不清
3b. He said yesterday she will come here this afternoon. 意思明確，與中文相等
3c. He said yesterday she would come here this afternoon. 時態一致原則。3b中的she還沒到，3c中的she可能到了，也可能沒到。3c 這句應該還有其它的意思。
時態這種玩意，脫離了語境就比較難辦。
家居三所
一般是一致原則，i think he is a good boy.
特殊的例如if引導的從句主將從現
you will be late if you get up late.
含有完成時的句子具體而定
he thought he had already finished .but he didn't.
再學習時候多記多積累就行了
