消防无线通信网宜采用单频单工和异频单工（半双工）调度指挥网的模式组网。
参考答案：对
两千多年前，古罗马哲学家西塞罗说：“谁控制了海洋，谁就控制了世界。”中国近代最早创建的几支海军是（ ）
①南洋 ②北洋 ③西洋 ④福建
A．①②③
B．①③④
C．②③④
D．①②④
The medicine ___ as soon as you take it. But it ____ the blood.
A．brings into effect; effects
B．takes effect; has a bad effect on
C．comes into effect; has little effect on
D．is carried into effect; has much effect on
