在( )组织结构中，命令具有多源性。

A．直线型

B．职能型

C．项目型

D．功能型

Both bus and tree topologies are characterized by the use of multipoint （1）. For the bus, all stations attach, through appropriate hardware （2）known as a tap, directly to alinear transmission medium, or bus. Full-duplex operation between the station and the tap allowsdata to be transmitted onto the bus and received from the （3）. A transmission from anystation propagates the length of the medium in both directions and can be received by all other（4）. At each end of the bus is a （5）, which absorbs any signal, removing it from thebus.

（3）是（）

A.tree

B.bus

C.star

D.ring