无线直放站的服务天线一般采用何种类型的天线。（）
A、全向天线
B、定向天线
C、抛物面天线
D、八木天线
参考答案：B
-–Do you think that we should make preparations for the competition in advance?
-–Exactly. ______.
A．Actions speak louder than words
B．Fight no battle unprepared
C．Better late than never
D．A good beginning is half done
把学校制度分为两个互不相通的轨道的学制是( )
A．单轨制
B．分支制
C．多轨制
D．双轨制
