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【单选题】
下列关于关系模式的码和外码的叙述中,( )是正确的 Ⅰ.主码可以是单个属性,也可以是属性组 Ⅱ.外码可以是单个属性,也可以是属性组 Ⅲ.一个关系模式的主码与该关系模式的任何一个外码的交一定为空 Ⅳ.一个关系模式的主码与该关系模式的所有外码一定包含了该关系模式的所有属性
A.
Ⅰ和Ⅱ
B.
Ⅰ、Ⅱ和Ⅲ
C.
Ⅰ、Ⅱ和Ⅳ
D.
Ⅰ、Ⅲ和Ⅳ
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参考答案:
举一反三
【判断题】在线路尽头处设置的是阻挡信号机,表示列车停车位置。
A.
正确
B.
错误
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【简答题】____ 是用竹紫或森素、铁素等为骨干相拼悬品起的大桥。多建于水流急、不易做桥墩的陡岸险谷,主耍见于西南地区。
查看完整题目与答案
【单选题】It takes an _________ of ten weeks for a house sale to be completed.
A.
on average
B.
averagely
C.
average
D.
averaged
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【单选题】Plato was a superb writer, and his works are part of the world's great literature. Most of his existing work is _______ dialogs and letters.
A.
in the name of
B.
in the face of
C.
in the charge of
D.
in the form of
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【简答题】Ten weeks _____ (be) needed to complete the task.
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【单选题】Plato was a superb writer, and his works are part of the world's great lierature. Most of his existing work is ______ dialogs and letters.
A.
in the form of
B.
in the from of
C.
in the matter of
D.
in the detail
查看完整题目与答案
【判断题】当 确定时, 越小,表明模型的拟合优度越好
A.
正确
B.
错误
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【判断题】测量器具误差是指测量器具本身固有的误差,也与外部条件有一定关系。
A.
正确
B.
错误
查看完整题目与答案
【单选题】Plato was a superb writer, and his works are part of the world’s great literature. Most of his existing work is ____ dialogs and letter.
A.
in the form of
B.
in terms of
C.
in the formation of
D.
in view of
查看完整题目与答案
【单选题】在线路尽头处设置的信号机是( )。
A.
防护信号机
B.
阻挡信号机
C.
出站信号机
D.
进站信号机
查看完整题目与答案
相关题目:
【判断题】在线路尽头处设置的是阻挡信号机,表示列车停车位置。
A.
正确
B.
错误
查看完整题目与答案
【简答题】____ 是用竹紫或森素、铁素等为骨干相拼悬品起的大桥。多建于水流急、不易做桥墩的陡岸险谷,主耍见于西南地区。
查看完整题目与答案
【单选题】It takes an _________ of ten weeks for a house sale to be completed.
A.
on average
B.
averagely
C.
average
D.
averaged
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【单选题】Plato was a superb writer, and his works are part of the world's great literature. Most of his existing work is _______ dialogs and letters.
A.
in the name of
B.
in the face of
C.
in the charge of
D.
in the form of
查看完整题目与答案
【简答题】Ten weeks _____ (be) needed to complete the task.
查看完整题目与答案
【单选题】Plato was a superb writer, and his works are part of the world's great lierature. Most of his existing work is ______ dialogs and letters.
A.
in the form of
B.
in the from of
C.
in the matter of
D.
in the detail
查看完整题目与答案
【判断题】当 确定时, 越小,表明模型的拟合优度越好
A.
正确
B.
错误
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【判断题】测量器具误差是指测量器具本身固有的误差,也与外部条件有一定关系。
A.
正确
B.
错误
查看完整题目与答案
【单选题】Plato was a superb writer, and his works are part of the world’s great literature. Most of his existing work is ____ dialogs and letter.
A.
in the form of
B.
in terms of
C.
in the formation of
D.
in view of
查看完整题目与答案
【单选题】在线路尽头处设置的信号机是( )。
A.
防护信号机
B.
阻挡信号机
C.
出站信号机
D.
进站信号机
查看完整题目与答案
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