单项选择题
A.has left hand twist
B.has inside threads on both ends
C.has outside threads on both ends
D.takes two men to operate
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（）.
单项选择题 A fire in a ballast pumproom can be brought under control with minimal impact on stability by（）.