单项选择题
A.should be passed close aboard on either side B.indicates that special caution is required C.is used at a channel bifurcation or junction D.is painted with red and white vertical stripes
A.easterly courses in high latitudes B.southerly courses in high latitudes C.westerly courses in low latitudes D.easterly courses in low latitudes that cross the equator
A.plane tangent at one point B.cylinder tangent at the equator C.cone tangent at one parallel D.infinite series of cones tangent at selected parallels