眾所周知, 定語從句可以分為限制性定語從句和非限制性定語從句。下面結(jié)合考例談?wù)剬W(xué)習(xí)運用非限制性定語從句時應(yīng)注意的幾個問題：
一、that不能用來引導(dǎo)非限制性定語從句。如：
【考例一】She heard the terrible noise, ________brought her heart into her mouth.
A. it B. which C. this D. that
【解析】選B。后半句為非限制性定語從句，盡管先行詞noise屬于事物，也不能用that而要用which來引導(dǎo)。which指代noise，在從句中作主語。
二、除which外，還可用when，where，whose，whom等引導(dǎo)非限制性定語從句，且各自的用法及差異與它們用在限制性定語從句時相同。如：
Next month, when you'll spend your summer holidays in your hometown, is approaching. 下個月即將來臨，屆時你們將在家鄉(xiāng)度暑假。(關(guān)系副詞when指代表示時間的名詞next month，并作從句的狀語。)
She is going to live in Macao, where she has some close friends. 她要到澳門去居住，在那里她有幾個密友。 (關(guān)系副詞where指代表示地點的名詞Macao，并在從句中作狀語。)
【考例二】Recently I bought an ancient Chinese vase, ________was very reasonable.
A. which price
B. the price of which
C. its price
D. the price of whose
【解析】選B。whose在從句中作表示所屬關(guān)系的定語，既可指代人，也可指代物。指物時，�？赊D(zhuǎn)換為of which；指人時�？赊D(zhuǎn)換為of whom。
【考例三】 In the office I never seem to have time until after 5:30 pm,______many people have gone home.
A. whose time B. that
C. on which D. by which time
【解析】 先行詞5:30 pm與time之間是一種同位關(guān)系，可用which來作定語替代。從句中的完成狀態(tài)，常與by短語連用。故選D。
三、在非限制性定語從句中作賓語的關(guān)系代詞不能省略。如：
He was eager to go to the hospital to see his stepmother, whom he loved as his own mother. 他迫切地想到醫(yī)院去看望他的繼母，他把繼母當(dāng)自己的親媽媽一樣愛戴。
四、非限制性定語從句的關(guān)系代詞which，既可以指代前面的先行詞，也可以指代前面整句的含義。如：
【考例四】 Dorothy was always speaking highly of her role in the play, of course,________made the others unhappy.
A. who B. which
C. this D. what
【解析】選B。指代“Dorothy總是高度評價自己在那場戲中所擔(dān)任的角色”的整個事件。
【考例五】Carol said the work would be done by October,________personally I doubt very much.
A. it B. that
C. when D. which
【解析】表示時間的名詞October，用“我個人非常懷疑”來修飾，意思不通。應(yīng)該修飾整個主句， 表示對“Carol說在十月前能做好這項工作”懷疑。故選D。
五、引導(dǎo)非限制性定語從句時as和which的差異：從句置于句首時，非限制性定語從句只能用as引導(dǎo)，而置于句末時，兩者都可以使用。 如：
【考例六】________is known to everybody, the moon travels round the earth once every month.
A. It B. As C. That D. What
【解析】逗號表明為非限制性定語從句。選B。
【考例七】________is mentioned above, the number of the students in senior high schools is increasing.
A. Which B. As
C. That D. It
【解析】答案為B。與考例六同理。
文/彭昊虹