【正确答案】 C

【答案解析】题干问：Figures showed that security screeners were—dangerous items．在危险物品方面，数据显示安检仪：选项A说能检测；B说不能检测；C说不能高效率地检测；而D说能很高效率地检测。根据原文：security screeners failed to detect knives 70%of the time，guns 30% of the time and simulated explosives 60% of the time．该题答案很容易判断应该为C。