单项选择题
（）is not a component of GPS.
A.He space component B.Control component C.User component D.Alarming component
单项选择题 （）is not an alarm required by IMO standards to be available on the ECDIS.
单项选择题 （）is not a factor which will affect the accuracy of GPS receiver.
单项选择题 （）is a digitized“picture”of a chart.
