— What bad weather !It rained again .

— Yeah, _____ when you walk to school .

A．mind you head

B．Keep of the grass

C．Watch your step

D．Be quiet

宽带VSAT车载站视频会议系统中，常用故障诊断方法为（）？

A.声音测试

B.色条测试

C.网络测试

D.回环测试