Unless by the police, you should keep silent over the accident.
A. asked
B. ask
C. being asked
D. having asked
网友回答
(答案→)A. asked
B. ask
C. being asked
D. having asked
解析：从by the police可以说明you与ask之间构成被动关系，故排除ＢＤ，另外非谓语动词的省略往往会省略从句的主语和部分谓语，即be动词，故选答案Ａ，也可以将状语从句补全，即Unless you are asked by the police,然后再去掉you are,即可得知答案。