常用于结构修饰的方法有（）.

A.成盐

B.成酰胺

C.加氢

D.氨甲基化

E.成几何异构体

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). A transmission from any station 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 the bus.

空白（1）处应选择（）

A.medium

B.connection

C.token

D.resource