单项选择题
A.complete the stroke，raise your oar slightly，swinging the oar slightly forward，and place it in the boat
B.lift the oar in a vertical position
C.complete the stroke and hold the oar out of the water
D.dip the blade of your oar into the water vertically and hold it perpendicular to the keel line
单项选择题 For a ship not on an international voyage，an approved substitute for an impulse projected rocket-type line throwing appliance is a（）.
单项选择题 Any vessel in need of carrying out deck washing must be（）by the department concerned beforehand.
单项选择题 An obstruction on a helideck is any object that might present a hazard to the（）.