Listen.Ihear _________.[ ] A.sing B.sing

痄腮患儿应隔离：（）

A.3～5天

B.5～10天

C.10～14天

D.14～21天

E.至腮肿消退

某动物每分钟能跑1800米，你知道它每小时能跑多少米吗？合多少千米？约是多少万米？

流感病毒发生变异的形式有

A．抗原转移、抗原漂移

B．抗原转移、抗原转换

C．抗原替换、抗原转换

D．抗原替换、抗原转移

E．抗原转换、抗原漂移

井下电缆为了区分电缆的额定电压，以颜色表示，36/6Kv电缆护套颜色为红色。

Both bus and tree topologies are characterized by the use of multipoint (16) ．For the bus，all stations attach，through appropriate hardware (17) 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 (18) ．A transmission from any station propagates the length of the medium in both directions and can be received by all other (19) ．At each end of the bus is a (20) ，which absorbs any signal，removing it from the bus．

A．medium

B．connection

C．token

D．resource