The ARPA may swap targets when automatically tracking if two targets（）

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.

A.manifold
B.remote pull box
C.discharge nozzle
D.machinery space

单项选择题When the ship is under attack by pirates,or terrorists,（）needs to be activated.

A.AIS
B.SSAS
C.SSP
D.SART

单项选择题Which of following physical abilities is not required as to the routine movement around a vessel?（）

A.Maintain balance and move with agility
B.Climb up and down vertical ladders and stairways
C.Open and close watertight doors
D.Take part in vessel evacuation procedures

单项选择题The information regarding ports such as buoyed channels,fairway,location and number of terminals,river channels,details of navigational marks,location of overhead bridges, underground cables etc. are shown in（）

A.small-scale charts
B.medium-scale charts
C.large-scale charts
D.natural scale charts