A) had been canceled
B) have been canceled
C) were canceled
D) having been canceled
第1题
无线电波分布在3Hz到3000GHz之间,在这个频谱内划分为()个带。
A.8
B.10
C.12
D.14
第2题
A.3Hz到3000GHz
B.1.5×10^6 GHz~3×10^7 GHz
C.8×10^5 GHz到3×10^8 GHz
D.3×10^8 GHz~3×10^10 GHz
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