单项选择题 A METHOD OF TOWING VESSELS THROUGH POLAR ICE BY MEANS OF ICEBREAKING TUGS WITH A SPECIAL STERN NOTCH SUITED TO RECEIVE AND HOLD THE BOW OF THE VESSEL TO BE TOWED defines（）.

单项选择题 A MARK OR POSITION AT WHICH A VESSEL IS REQUIRED TO REPORT TO ESTABLISH ITS POSITION defines（）.

单项选择题 （）will the discharging operations take?