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【单选题】
将表中的字段定义为“( )”，其作用使字段中的每一个记录都必须是惟一的以便于索引。A.
索引
B.
主键
C.
必填字段
D.
有效性规则
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举一反三
【单选题】劣等商品的价格下降而其他情况不变的时候
A.
替代效应和收入效应相互加强，导致该商品的需求量增加
B.
替代效应和收入效应相互加强，导致该商品的需求量减少
C.
替代效应倾向于增加该商品的需求量，而收入效应倾向于减少其需求量
D.
替代效应倾向于减少该商品的需求量，而收入效应倾向于增加其需求量
【单选题】I want an ice cream cone. A. simple sentence B. Compound sentence C. Complex sentence
A.
simple sentence
B.
Compound sentence
C.
Complex sentence
【单选题】对劣等品的价格下降而其他情况不变的时候,有:
A.
替代效应和收入效应相互加强导致该商品的需求量增加
B.
替代效应和收入效应相互加强导致该商品的需求量减少
C.
替代效应倾向于增加该商品需求量，而收入效应倾向于减少其需求量
D.
替代效应倾向于减少该商品需求量，而收入效应倾向于增加其需求量
【单选题】He did not have to go after her, biut he did. A. Simple sentence B. Compound sentence C.Complex sentence D. Complex-Compound sentence
A.
Simple sentence
B.
Compound sentence
C.
Complex sentence
D.
Complex-Compound sentence
【单选题】He is the author who spoke to us, and we have never forgotten that experience. A. Simple sentence B. Compound sentence C. Complex sentence D. Compound-Complex sentence
A.
Simple sentence
B.
Compound sentence
C.
Complex sentence
D.
Compound-Complex sentence
【单选题】Your actions set a bad example for others, and you need to change your ways. A. Simplle sentence B. Compound sentence C. Complex sentence D. Compound-Complex sentence
A.
Simplle sentence
B.
Compound sentence
C.
Complex sentence
D.
Compound-Complex sentence
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