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

单项选择题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

单项选择题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

单项选择题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)

单项选择题The radar control that reduces weak echoes out to a limited distance from the ship is the（）.

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

单项选择题The officer of the watch should use radar when appropriate and at all times in（）waters.

A.congesting
B.congested
C.congestion
D.congest