单项选择题
A chart position enclosed by a square is a（n）（）.
A.fix B.estimated position C.dead reckoning position D.running fix
单项选择题 （）is not a position-fixing system.
单项选择题 Which aid is NOT marked on a chart with a magenta circle? （）
单项选择题 When using a Lambert conformal chart in high latitudes，angles such as bearings are measured in reference to （）.
