列式计算．

（1）121乘9的积减去1000，再扩大20倍，结果是多少？

（2）一个数是2的倍数，同时也是3的倍数，还是5的倍数，这个数最小是多少？

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