像句子My dad's got a camera that takes photos unger water.先行詞 a camera是單數,從句that takes photos unger water的謂語動詞就用takes
再如：The boys who are from America like China.這裡主句是The boys like China.定語從句who are from America 修飾先行詞the boys.因為the boys 是複數,所以定語從句who are from America 的謂語動詞用複數are
如果還不明白,你可以倒過來做：把 1）The boys like China 2）THe boys are from America 兩句改成定語從句.那麼答案就是The boys who are from America like China
附：關係副詞引導的定語從句關係副詞可代替的先行詞是時間、地點或理由的名詞，在從句中作狀語。
1）when, where, why
關係副詞when, where, why的含義相當於介詞+ which結構，因此常常和介詞+ which結構交替使用，例如：
There are occasions when （on which） one must yield. 任何人都有不得不屈服的時候。
Beijing is the place where （in which） I was born. 北京是我的出生地。
Is this the reason why （for which） he refused our offer? 這就是他拒絕我們幫助他的理由嗎？
2）that代替關係副詞
that可以用於表示時間、地點、方式、理由的名詞後取代when, where, why和介詞+ which引導的定語從句，在口語中that常被省略，例如：
His father died the year （that / when / in which） he was born. 他父親在他出生那年逝世了。
He is unlikely to find the place （that / where / in which） he lived forty years ago. 他不大可能找到他四十年前居住過的地方。
同位語從句講解與練習
1．定義：用作同位語的從句叫做同位語從句。
2.用法：同位語從句的先行詞多為fact, news, idea, thought, question, reply, report, remark等，關聯詞多用從屬連詞。如： 1. 連詞that引導同位語從句
（注：引導同位語從句的不能省略）
The idea that you can do this work well without thinking is quite wrong.你認為不動腦筋就能做好這件工作的想法是完全錯誤的。（作idea的同位語）
【注意1】在某些名詞(如demand, wish, suggestion, resolution等)後面的同位語從句要用虛擬語氣
There was a suggestion that Brown should be dropped from the team. 有一項建議是布朗應該離隊。
【注意2】引導同位語從句的連詞that通常不省略
He gabbed his suitcase and gave the impression he was boarding the Tokyo plane. 他拿起了手提箱，給人的印象是他要登上飛往東京的飛機了。
2. 連詞whether引導同位語從句 （注：if不能引導同位語從句）
The question whether we should call in a specialist was answered by the family doctor. 我們是否請專家由家庭醫生來定。
附：其它引導詞引導的同位語從句連線代詞what, who, whom, whose, which引導同位語從句
1).I have no idea what size shoes she wears.我不知道她穿幾號的鞋。（what作定語）
2).I have no idea which wine is best—it’s a matter of personal taste.我不知道哪種酒最好，這是個人口味的問題。（which作定語）
3) question who will take his place is still not clear. （who作主語）
4. 連線副詞引導同位語從句 連線副詞when, where, how, why
We haven’t yet settled the question where we are going to spend our summer vacation.
1．that引導的同位語從句與定語從句之區別
that引導的同位語從句/that引導的定語從句
1）句法
that只起連線從句的作用，無意義。在從句中不充當句子成分。不可省。
that替代先行詞在從句中不僅起連線作用，還充當一個句子成分。如在從句中作動詞的賓語時可省略。
2）意義上
從句是被修飾名詞的內容。從句起限定作用，是定語
The news that Mr. Li will be our new English teacher is true. (同位語從句，that不可省)
The news (that) he told me yesterday is true. (定語從句，that在從句中作的賓語，可省)
2．一些表示“建議、命令、要求”的名詞後所跟的同位語從句中，謂語動詞用虛擬語氣should+動詞原形表示。should可省。如：
This is our only request that this (should) be settled as soon as possible.
