In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.

To a router, a flow is a (71) of packets that share the same characterstics, such as traveling the same (72) , using the same (73) , having the same kind of security, and so on. A router that supports the handling of flow labels has a (74) table. The table has an entry for each Active flow label; each entry defines the (75) required by the corresponding flow label.

（75）是（）

A.quality

B.Traffic

C.services

D.route

金属切割机是一种磨削()工具。

（A）专用 

（B）破拆 

（C）液压 

（D）扩张