Navigational charts are （） frequent changes，the important one of which are promulgated by Admiralty Notices to Mariners．

A.with
B.from
C.on
D.by

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