GSM900系统,其上下行信号的频率间隔为()
A.30MHZ
B.40MHZ
C.45MHZ
D.50MHZ
参考答案:C
—I passed the last exam yesterday. —Oh, you’re really a ()(幸运) dog.
右图中,从山峰向下望,将不能看见哪一点()
A.A点
B.B点
C.C点
D.D点