All of the following statements about digital time stamps are true except（）
A. The digital timestamp is provided by the DTS service organization
B. Time-stamped files can be modified
C. The digital time stamp is used exclusively to prove the time the message was sent
D. It is not possible to timestamp a file with a date and time different from the current date and time
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E-commerce can be divided into__ based on the transaction degree（）
A. B2B, B2C, C2C and B2G
B. Internet e-commerce, Intranet e-commerce, extranet e-commerce and mobile commerce
C. EDI-based e-commerce and non-EDI e-commerce
D. Complete e-commerce and incomplete e-commerce
In short, e-commerce is__ carried out on the Internet using modern information technology（）
A. Express delivery service
B. Customer service
C. Marketing activity
D. Trading activity
In the following descriptions of the framework of e-commerce, which one is not true（）
A. The architecture of e-commerce include: hardware platform, network platform, software platform, and business service support platform
B. The application of e-commerce includes market e-commerce, enterprise e-commerce and social e-commerce
C. Public policies, laws and credit systems are the pillars of the e-commerce framework
D. Technical standards and security are the pillars of the e-commerce framework
The basic types of B2B e-commerce do not include__（）
A. seller’s market model
B. trading market model
C. buyer’s market model
D. subscription model
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