单项选择题
Vapor given off by a flammable liquid will burn when ignited provided（）
A.the vapor and air mixture is too rich B.it is mixed with certain proportions of air C.the vapor is too little compared to the air D.it is of heavy toxicity
单项选择题 Fixed piping leads from the（）to various areas of the compartment to be flooded.
单项选择题 When the ship is under attack by pirates,or terrorists,（）needs to be activated.
单项选择题 Which of following physical abilities is not required as to the routine movement around a vessel?（）
