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單項(xiàng)選擇題

The radiotelegraph alarm signal is（）.

A.SOS sent three times
B.ten one-second dashes with a four-second interval between them
C.twelve four-second dashes with a one-second interval between them
D.twelve one-second dashes with a short interval between them

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單項(xiàng)選擇題

The expression FIRST MAGNITUDE is usually used to refer only to bodies of magnitude（）.

A.1.5 and greater
B.1.25 and greater
C.1.0 and greater
D.0.5 and greater

單項(xiàng)選擇題

The expression DROP ANCHOR means（）.

A.hold anchor
B.leave anchor
C.let go anchor
D.weigh anchor