專升本英語名詞性從句是經(jīng)常考到的知識點之一，名詞性從句有主語從句、表語從句、同位語從句等，今天庫課小編要給大家分享的是專升本英語表語從句講解，有需要的考生可以看看。
表語：
說明主語的性質(zhì)、特征、狀態(tài)或身份，說明主語是什么或者怎么樣?？傊碚Z是對主語的解釋和說明，是主語具體化，并且常與連系動詞一起使用。
表語從句：
在復(fù)合句中作表語的從句, 就叫做表語從句。表語從句一般放在系動詞之后，結(jié)構(gòu)是“主語+系動詞+表語從句”。
連系動詞：
be動詞
表示持續(xù)的系動詞(keep, remain, stay)
感官動詞feel(摸起來，感覺) , smell(聞起來) , sound(聽起來) , taste(嘗起來，吃起來) 等
表示變化的系動詞(become, grow, turn, fall, get, go,)
表終止的系動詞prove, turn out(結(jié)果是，證明是)、seem, appear(看起來……)
連系動詞通常不用于被動語態(tài)和進行時態(tài)中。
He has become what he wanted to be ten years ago.
他已經(jīng)成為了他10年前想成為的樣子。
His suggestion is that we should stay calm.
他的建議是，我們應(yīng)該保持冷靜。
一、表語從句的引導(dǎo)詞
1.從屬連詞
that / whether /as if /as though/as/because
(1) that引導(dǎo)表語從句本身沒有詞義，在句中只起連接作用，不充當句子成分，一般不能省略。
That fact is that more than seventy percent of the earth’s surface is covered by water.
連接詞that一般不能省略，但當主句中含動詞do的某種形式時，that可以省略。
What I want to do is (that) I can go up to him and thank him. 我想做的事是走到身邊去感謝他。
(2) whether引導(dǎo)表語從句表示“是否”,但不充當句子的成分。
The question is whether we can finish our work by tomorrow evening.
if 與whether均意為“是否”，但引導(dǎo)表語從句時，只能用whether, 不能用if。
(3)as if/though“好像”，引導(dǎo)表語從句時要注意語態(tài)。
如果句中的情況與事實不相符，從句多用虛擬語氣。如果從句表示與現(xiàn)在事實相反,謂語動詞用一般過去式;如果從句表示與過去事實相反時,謂語動詞要用“had + 過去分詞 ”，如果從句表示將來的可能性不大，用would (might ,could )+動詞原形。
Li Lei is now in a new jacket. He looks as if he were an American boy. (現(xiàn)在事實相反)
The girl is giving us a vivid description of the moon. It seems as if she had been to the moon many times. (與過去事實相反)
It looks as if it might rain. (與將來事實相反)
但是，如果as if/though引導(dǎo)的表語從句所表示的與事實相符，從句則用陳述語氣。
The clouds are gathering. It looks as if is going to rain.
(4) as引導(dǎo)表語從句
He looked just as he had looked ten years before.
他看起來還與十年前一樣。
(5) because引導(dǎo)表語從句
常用結(jié)構(gòu)：This/That/It is/was because...
That is because I don’t like Chinese.
2.連接代詞
who/whom/whose/what/which/whoever/whatever/whichever/whomever，在表語從句中做主語、賓語、表語和定語。
Tom is no longer what he used to be. (what做表語)
The problem is who is fit for this job. (who做主語)
This is what I want to tell you. (what做賓語)
The problem is whose work is the best. (whose做定語)
3.連接副詞
when/where/how/why，在表語從句中做狀語。
The question is how he did it. 問題是他是如何做此事的。
The question is where we can live.問題是我們能住在哪兒。
二、特例強調(diào)
1.reason做主語或主語中包含事件的起因時,后面的表語從句表示原因時要用that來引導(dǎo),而不用because;why引導(dǎo)主語從句做主語時，表語從句用that引導(dǎo)，不用because。
The reason is that he got up late.
Why he is late is that he got up late.
2.that is why/because
?、賂hat is why ...是常用句型,其中why引導(dǎo)的從句在句中作表語,該句型通常用于針對前面已經(jīng)說過的原因進行總結(jié)。That is the reason why ...與That is why ...是同義的，“這就是……的原因/因此……”，但是從語法結(jié)構(gòu)上講That is the reason why ...中的why引導(dǎo)的是一個定語從句。
That is why she failed to pass the exam.
那就是她考試不及格的原因。(why 在表語從句中充當原因狀語)
That is the reason why she failed to pass the exam.
那就是她考試不及格的原因。(why 在定語從句中充當原因狀語)
②That is because...句型中從屬連詞because引導(dǎo)的名詞性從句在此作表語，這也是個常用句型，意為“這就是因為……”。
That is because I got up late. 這是因為我起床遲了。
?、邸癟hat is because...”與“That is why...”之間的不同在于“That is because...”指原因或理由， “That is why...”則指由于各種原因所造成的后果。
I was angry. That was because he didn’t understand me.我生氣是因為他不理解我。(表語從句強調(diào)原因)
That’s why he got fired from that firm.那正是他被公司解雇的原因。(表語從句強調(diào)結(jié)果)
3.The reason (why.../for...)is /was that... “...的原因是...”
The reason for his absence is that he got up late.
The reason why he is absent is that he got up late.
他缺席的原因是他起床遲了。
4.使用虛擬語氣的表語從句
在表示建議、勸告、命令、計劃含義的名詞后的表語從句，謂語動詞需用“should+動詞原形”表示虛擬語氣，should可省略。常見的詞有：advice，suggestion，order，request，proposal，plan，idea等。
My suggestion is that we (should) start early tomorrow.我的建議是我們明天一早就出發(fā)。
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