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问题 选择题

下列反应能用Ca2++ CO32－=CaCO3↓ 表示的是（   ）                 

A．澄清石灰水中通入CO2

B．Ca(NO3)2溶液和Na2CO3溶液混合

C．CaCl2溶液和BaCO3

D．澄清石灰水和Na2CO3溶液混合

答案

BD

单项选择题

TCP/IP (71) layer protocols provide services to the application (72) running on a computer. The application layer does not define the application itself, but rather it defines (73) that applications need — like the ability to transfer a file in the case of HTTE In short, the application layer provides an (74) between software running on a computer and the network itself. The TCP/IP application layer includes a relatively large number of protocols, with HTTP being only one of those. The TCP/IP (75) layer consists of two main protocol options — the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).

A．application

B．session

C．physical

D．transport
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单项选择题

Please come and help me with this form because I don't know how to______it.

A．set about

B．set aside

C．set off

D．set up
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