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【单选题】
不允许记录中出现重复索引值的索引是A.
主索引
B.
主索引、候选索引和普通索引
C.
主索引和候选索引
D.
主索引、候选索引和唯一索引
拍照语音搜题，微信中搜索"皮皮学"使用
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知识点：
皮皮学刷刷变学霸
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【简答题】高速铁路四跨绝缘锚段关节检修周期为____年。
【简答题】高速铁路四跨非绝缘锚段关节检修周期为____年。
【单选题】Certified Cargo Screening Facilities are charged with ___.
A.
randomly selecting about twenty percent of all air cargo, and inspect these shipments before they are loaded on any aircraft
B.
conducting background checks for all airlines and airport employees who are in contact with international cargo air shipments
C.
conducting one-hundred-percent inspections of all shipments that will eventually travel on passenger aircraft
D.
reporting on suspicious cargo shipments originating from abroad, through a program called “Automated Targeting System”