Food safety is one of the problems now all over the world.
A. discussed
B. to be discussed
C. being discussed
D. having been discussed
网友回答
A. discussed
B. to be discussed
(答案→)C. being discussed
D. having been discussed
解析：考查分词做定语。本句中的动词discuss与名词problems之间构成被动关系，因为本句有now说明这个问题正在被讨论，用现在分词的被动语态。句意：现在食品安全是一个全世界都正在讨论的问题。故C正确。