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问题 选择题

76.8mg铜与适量浓硝酸反应，铜全部作用后，如果NO3-离子减少2×10-3mol，则溶液中H+离子同时减少                        （  ）

A．4.8×10-3mol

B．4.4×10-3mol

C．3.2×10-3mol

D．2.2×10-3mol

答案

答案：B

单项选择题

A glue that holds the whole Internet together is the network layer protocol, (1) .Unlike most older network layer protocols, it was designed from the beginning with internetworking in mind. Its job is to provide a (2) way to transport data grams from source to destination, without regard to whether these machines are on the same network or whether there are other networks in between them.

Communication in the Internet works as follows. The (3) layer takes data streams and breaks them up into data grams. Each datagram is transmitted through the Internet, possibly being fragmented into smaller units as it goes. When all the pieces finally get to the destination machine, they are reassembled by the (4) layer into the original datagram. This datagram is then handed to the transport layer, which inserts it into the receiving process’ input stream.

An IP datagram consists of a header part and a text part. The header has a (5) part and a variable length optional part.

2（）

A．best-quality

B．quality-guaranteed

C．connection-oriented

D．best-efforts
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选择题

科学家用计算机模拟后确认，60个N原子可结合成N60分子．下列关于N60的叙述中正确的是　  [ ]

A． N60是一种新型的化合物

B． 一个N60分子中含有30个N2分子　

C． N60的相对分子质量为840

D． N60和N2混合后形成的是纯净物
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