填空传输媒体总体上可以分为两大类,其中双绞线、同轴电缆和光纤属于____型传输媒体。
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填空无线电微波通信在数据通信中占有重要地位。微波在空间主要是直线传播。传统的微波通信主要有两种方式,即____和卫星通信。
_________he is still working on the project, I do not mind when he will finish it.
A. In case
B. As long as
C. Even if
D. As far as
3). He bought an expensive coat ___________ he had no job.
A. since
B. although
C. who
D. however
The goods _____________ when we arrived at the airport.
A. were just unloading
B. were just being unloaded
C. had justunloaded
D. werejust unloaded