单项选择题
A.Set B.Frequency C.Period D.Function
The recording fathometer produces a graphic record of t...
单项选择题The recording fathometer produces a graphic record of the（）.
A.bottom contour only up to depths of 100 fathoms B.depth underneath the keel against a time base C.contour of the bottom against a distance base D.depth of water against a distance base
The points on the earth’s surface where the magnetic di...
单项选择题The points on the earth’s surface where the magnetic dip is 90° are（）.
A.Along the magnetic equator B.Connected by the isoclinal line C.The isopors D.The magnetic poles
The four standard light colors used for lighted aids to...
单项选择题The four standard light colors used for lighted aids to navigation are red，green，white，and （）.
A.purple B.orange C.blue D.yellow
