单项选择题
The ARPA may swap targets when automatically tracking if two targets（）
A.are tracked on reciprocal bearings B.are tracked at the same range C.are tracked on the same bearing D.pass closely to each other
单项选择题 Vapor given off by a flammable liquid will burn when ignited provided（）
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.
