单项选择题
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（）.
单项选择题 The radar control that reduces weak echoes out to a limited distance from the ship is the（）.
单项选择题 The officer of the watch should use radar when appropriate and at all times in（）waters.