单项选择题 The word “critical” in the sentence “This is a critical period as any loss of propulsion, or steering, can lead to collision, grounding, or other damage to the ship” can be best replaced by （）.

单项选择题 “Any leaks in piping, propeller shaft, machinery, tanks, will have to be repaired, or at least patched up temporarily until the next stop” This sentence means that （）.

单项选择题 “In times of heavy weather, it is extremely dangerous if manning is very short” This sentence means （）.