单项选择题
A Doppler speed log indicates speed over ground（）.
A.at all times B.in the bottom return mode C.in the volume reverberation mode D.only when there is no current
单项选择题 A double male coupling is one that（）.
单项选择题 A fairly accurate estimation of a ship’s position can be calculated by a technique known as（）.
单项选择题 A fire has broken out on the stern of your vessel. You should maneuver your vessel so the wind（）.
