单选题 Both bus and tree topologies are characterized by the use of multipoint ______. For the bus, all stations attach, through appropriate hardware ______ 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 ______. A transmission from anystation propagates the length of the medium in both directions and can be received by all other______. At each end of the bus is a ______, which absorbs any signal, removing it from thebus.