請(qǐng)看這道題，這個(gè)until 后要接過去分詞嗎?
He is a man of few words, and seldom speaks until _________ to.
A. spoken B. speaking C. speak D. be spoken
【分析】此題容易誤B，認(rèn)為until 是介詞，后接動(dòng)詞時(shí)用動(dòng)名詞形式。其實(shí)，此題應(yīng)選A，until spoken to 為 until he is spoken to 之省略。句意為“他是個(gè)沉默寡言的人，別人不同他說(shuō)話，他很少同別人說(shuō)話”。按英語(yǔ)習(xí)慣，一些表示時(shí)間、地點(diǎn)、條件、方式、 讓步等的狀語(yǔ)從句，若其主語(yǔ)與主句主語(yǔ)一致，且從句謂語(yǔ)包含動(dòng)詞be, 那么可將從句的主語(yǔ)和動(dòng)詞be省略：
You must study hard while (you are) young, or you will regret when (you are) old. 趁年輕時(shí)要努力學(xué)習(xí)，不然到老了你會(huì)后悔的。
I won't go unless (I am) invited. 我不會(huì)去, 除非請(qǐng)我。
Look out for cars when (you are) crossing the streets. 過馬路時(shí)要注意汽車。
While (I was) waiting I was reading some old magazines. 等的時(shí)候我在看一些舊雜志。
He worked very hard though (he was) still rather poor in health. 盡管身體還不好，但他仍努力工作。
He will work hard wherever (he is) sent by the Party. 無(wú)論黨把他派往哪里,他都會(huì)努力工作。
請(qǐng)?jiān)倏磧傻涝囶}：
(1) If carefully _________, the experiment will be successful.
A. do B. does C. done D. doing
答案選C，可視為 if it is carefully done 之省略。
(2) The research is so designed that once _________ nothing can be done to change it.
A. begins B. having begun C. beginning D. begun
答案選D，可視為 once it is begun 之省略。
