Question

Unless _________ by the police, you should keep silent over the accident.

1. A.
   asked
2. B.
   ask
3. C.
   being asked
4. D.
   having asked

Answer 1

A
試題分析：從by the police可以說(shuō)明you與ask之間構(gòu)成被動(dòng)關(guān)系，故排除ＢＤ，另外非謂語(yǔ)動(dòng)詞的省略往往會(huì)省略從句的主語(yǔ)和部分謂語(yǔ)，即be動(dòng)詞，故選答案Ａ，也可以將狀語(yǔ)從句補(bǔ)全，即Unless you  are asked by the police,然后再去掉you are,即可得知答案。
考點(diǎn)：考查非謂語(yǔ)動(dòng)詞的省略。
點(diǎn)評(píng)：狀語(yǔ)從句的省略同時(shí)具備下列兩個(gè)條件:①主句和從句的主語(yǔ)一致，或從句主語(yǔ)為it；②從句主要?jiǎng)釉~是be的某種形式。從句中的主語(yǔ)和be動(dòng)詞常可省略