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單項(xiàng)選擇題

The shoreline along Rocky Point should give a good radar return because（）.

A.the shore is bluff and rocky
B.of offshore exposed rocks
C.submerged reefs cause prominent breakers
D.the lookout tower is marked with radar reflectors

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單項(xiàng)選擇題

The radio waves used for radar are very short，only（）long.

A.a few centimeters
B.a few fathoms
C.a few meters
D.a few feet

單項(xiàng)選擇題

The radar control used to reduce sea return at close ranges is the（）.

A.gain control
B.sensitivity time control
C.fast time constant
D.pulse length control