A. aren’t allowed B. have allowed C. allowed D. allow
分析：看到allow 就要想到短语allow sb. to do sth. “允许某人做某事”。而里面的某人做主语了，所以这儿应该是被动语态，正确答案是A。
巩固练习：
1、That dictionary is useful yo me. So I ________ 85 yuan for it.
A. spent B. paid C. took D. cost
2、The old man’ lesson was too boring, but I ________ during the class.
A. try to sleep B. tried to sleep C. try not to sleep D. tried not to sleep
3、 —Which MP4 would you like to buy, this one or that one?
—________, I don’t like them at all.