When you e into the exhibition hall，you can see a large board with a notice on it，saying visitors not to touch the exhibits.
A. will request
B. request
C. are requesting
D. are requested
网友回答
A. will request
B. request
C. are requesting
(答案→)D. are requested
解析：“request sb.(not)to do sth.要求某人(不要)做某事”是固定结构,根据题干,应使用被动语态。