产道的组成，不包括（）。

A.子宫体

B.子宫下段

C.子宫颈

D. * *

E.骨盆底软组织

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 a linear transmission medium, or bus. Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received from the(3).Atransmission from any station propagates the length of the medium in both directions and can be received by all other(4).At each end ofthe bus is a(5),which absorbs any signal, removing it from the bus．

空白（2）处应选择（）

A.processing

B.switching

C.routing

D.interfacing