平均值远左离(右离)直方图的中间值，频数自左至右减少(增加)，直方图不对称。这种直方图是( )直方图。

A．偏峰型

B．陡壁型

C．双峰型

D．孤岛型

For each blank, choose the best answer from the four choices and write down on the answer sheet.
(71) is a professional organization of individuals in multiple professions which focuses on effort on lower-layer protocols.
(72) is the popular backbone technology for transmitting information at high speed with a high level of fault tolerance which is developed under the direction of ANSI.
(73) functions with two layers of protocols. It can connect networks of different, speeds and can be adapted to an environment as it expands.

A. The hub B. The bridgeC. The routerD. The proxy

A socket is composed of two addresses: (74) .Heterogeneous network environments consist of computer systems from (75) vendors that run different operating systems and communication protocols.