在大型建筑物的低层、地下商场、地下停车场等环境下,移动通信信号弱,手机无法正常使用,形成了移动通信的()和()。
A.切换区域
B.盲区
C.拥塞区域
D.阴影区
参考答案:B, D
— Why didn't you call him yesterday?
— I him ,but the line was busy. [ ]
A. do call
B. did call
C. was calling
D. had called
下列哪种病不是因激素分泌异常所引起的( )
A.糖尿病
B.贫血
C.大脖子病
D.甲亢