ISPS规则要求缔约国政府（船旗国主管机关）：（）I、规定适当的保安等级；II、批准船舶保安计划；III、向以审核符合SOLAS公约和ISPS规则的船舶签发ISSC；IV、向IMO及航运业和港口业通报信息。

A.I~III

B.I、II、IV

C.I~IV

D.I、II

Sometimes an ad can lead you to buy something you don't need at all. "Sometimes" means______.       [ ]

A. at times                    

B. at other times      

C. at the same time              

D. at a time