单项选择题
There are some back-up satellites in the event of failure. If the operational satellite is out of work,（）.
A.communications in the whole system will stop
B.the global system will be damaged
C.the back-up one will take its place
D.the whole system will not work
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相关考题
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单项选择题
The satellites over the major ocean regions cover the globe（）.
A.besides the polar regions
B.including the North Pole and the South Pole
C.above 70N and below 70S
D.as far north and south 70 -
单项选择题
（）is a space system using one or more artificial earth satellites.
A.satellite network
B.Satellite Link
C.INMARSAT
D.Satellite System -
单项选择题
The establishment of INMARSAT as an independent organization marked a great step forward for maritime radio communications. What does “marked a great step” mean in the sentence?（）
A.To run faster than ever
B.To go forward
C.To march without stopping
D.A significant symbol of a great improvement in maritime communication
