单项选择题
A.Your speed must be reduced to bare steerageway
B.A look-out is not required if the radar is on
C.Fog signals are only required when a vessel is detected by radar
D.The radar should always be kept on a short-range scale
单项选择题 You are underway in restricted visibility and hear a fog signal forward of the beam. Nothing appears on your radar screen. You must（）.
单项选择题 You are underway at 5 knots and see on your radar a contact 10 miles directly astern of you. 12 minutes later，the contact is 8 miles directly astern of you. What is the estimated speed of the contact? （）
单项选择题 You are scanning the radar screen for a buoy fitted with racon. How should this signal appear on the PPI display?（）