单项选择题 An inflatable liferaft is floating in its container，attached to the ship by its painter，as the ship is sinking rapidly. Which action should be taken with respect to the liferaft container? （）

单项选择题 An indirect radar echo is caused by a reflection of the main lobe of the radar beam off the observer’s vessel. Which of the following is NOT a characteristic of indirect echoes? （）

单项选择题 An icebreaker may use the code letter “K” to remind ships of their obligation to listen continuously on their radio. This signal may be made by any of the following EXCEPT（）.