单项选择题
Which chart symbol indicates the bottom is clay（）.
A.Cly B.Cla C.Cl D.C
单项选择题 Where would you obtain data on currents for areas of the world not covered by the National Ocean Service（）.
单项选择题 The soundings on the imperial chart are measured in（）.
单项选择题 The short-long dashed，magenta lines parallel to York River Entrance Channel mark（）．
