單項(xiàng)選擇題

General communications are those communications（）.

A.between ship stations and shore-based communication networks
B.concern the management and operation of ships
C.may have an impact of the safety on ships
D.all of A, B, C

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單項(xiàng)選擇題

What’s the advantage when using the satellites?（）

A.The message can be directed to the desired location
B.The message can follow the earth‟s curvature
C.The quality of message can not be affected by climatic
D.the range of the message extend and the quality of reception is improved

單項(xiàng)選擇題

Some radio waves（）the surface of the earth because of its（）.

A.are capable of following / distance
B.can follow / altitude
C.can hardly follow / shape
D.are unable following / angle