My position has been obtained （） astronomical observation．

A.found in the center(s) of the compass rose(s)
B.indicated by isogonic lines
C.found in a note on the chart
D.All of the above

A.red triangle with the letter R
B.white triangle with the letters RG
C.green square with the letter G
D.white square with the letters GR

A.latitude scale near the middle of the track line
B.longitude scale near the middle of the track line
C.latitude scale at the midlatitude of the chart
D.latitude or longitude scale at the middle of the scale