The X. 25 standard specifies three layers of functionality. Which layers of the OSI model
A. the Data Link, Network and Session Layers
B. the Physical, Data Link and Network Layers
C. the Physical, Data Link and Transport Layers
D. the Session Layers, Network Layers and Presentation Layers
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确定一个货物买卖合同是否具有国际性,关键是要确定当事人的国籍,代表处机构所在地的处所往往也被视为通常意义上的“营业地”。()
A. 正确
B. 错误
【C14】
A. whole
B. all
C. present
D. entire
Let R and S be the relation respectively:
The number of tuples that the result of the expression R co S (Here is the natural join of relations R and S) is
A. 3
B. 4
C. 6
D. 9