单项选择题
A polyconic projection is based on a （）.
A.plane tangent at one point B.cylinder tangent at one parallel C.cone tangent at one parallel D.series of cones tangent at selected parallels
单项选择题 A pilot vessel on pilotage duty at night will show sidelights and a stern light （）.
单项选择题 A pilot vessel may continue to sound an identity signal if she is （）.
单项选择题 A pilot chart does NOT contain information about （）.
