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

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

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The radar control that shortens all echoes on the display and reduces clutter caused by rain or snow is the（）.

A.sensitivity time control (sea clutter control)
B.receiver gain control
C.brilliance control
D.fast time constant (differentiator)

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