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? （）
A.Dead in the water B.1 knot C.10 knots D.15 knots
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?（）
单项选择题 Which statement is true concerning a vessel equipped with operational radar?（）.
单项选择题 Which statement is TRUE concerning a vessel equipped with operational radar?（）.
