单项选择题
A low HDOP (Horizontal Dilution of Precision) number such as 2 indicates a （）.
A.poor fix B.good fix C.poor signal quality D.good signal quality
单项选择题 A list signal of one white light indicates that the vessel is （）.
单项选择题 A list man would expect to see any of the following light signals except （）.
单项选择题 A line of position from a celestial observation is a segment of a （）.
