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【多选题】
账簿按用途分，可以分为（）。A.
备查账簿
B.
分类账簿
C.
卡片式账簿
D.
序时账簿
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皮皮学刷刷变学霸
举一反三
【单选题】Economic models
A.
are essentially different from those used in other sciences.
B.
always use graphs.
C.
simplify reality.
D.
include all relevant facts.
【单选题】We can infer that current virtual reality devices ______.
A.
still need improving to create a perfect virtual world
B.
are already perfect to create a virtual world
C.
are unable to create a virtual world
D.
are harmful to users of virtual reality
【简答题】在数据库技术中使用数据模型的概念来描述数据库的结构和语义。数据模型有概念数据模型和结构数据模型两类，实体联系模型(E-R模型)是【 】数据模型。
【单选题】Traditional economic models found it hard to explain the phenomenon of .
A.
search frictions
B.
unemployment
C.
labor as commodity
D.
wage falls
【单选题】Economic models
A.
cannot be useful if they are based on false assumptions.
B.
were once thought to be useful, but that is no longer true.
C.
must incorporate all aspects of the economy if those models are to be useful.
D.
can be useful, even if they are not particularly realistic.
【单选题】Economic models
A.
are not useful because they omit many real-world details.
B.
are usually composed of diagrams and equations.
C.
are useful because they do not omit any real-world details.
D.
contribute very little to economists’ understanding of the real world.
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