单项选择题
The（）transmits own ship data cyclically via two defined VHF channels and receives the same data of the other ships and objects that are equipped with AIS systems.
A.AIS B.ECDIS C.GPS D.VDR
单项选择题 Radar makes the most accurate determination of the（）.
单项选择题 Most modern Loran-C receivers，when not tracking properly，have a（n）（）.
单项选择题 Loran-C uses the multiple pulse system because（）.
