A V-shaped ripple with the point of the V pointing upstream in a river may indicate a ______.(1.0)
A.submerged rock, not dangerous to navigation B.broken wreck, not dangerous to navigation C.towed-under buoy D.all of the above正确答案C
A V-shaped ripple with the point of the V pointing upstream in a river may indicate a ______.(1.0)
A.submerged rock, not dangerous to navigation B.broken wreck, not dangerous to navigation C.towed-under buoy D.all of the above正确答案C
