A white buoy with an orange rectangle on it displays（）.

A.danger
B.vessels are excluded from the area
C.the buoy is a mooring buoy
D.operating restrictions are in effect

A.an isolated danger mark
B.a hydrographic data collection buoy
C.a mooring buoy
D.marking a restricted area

A.submerged rock，not dangerous to navigation
B.sunken wreck，not dangerous to navigation
C.towed-under buoy
D.All of the above