单项选择题 The issue of Notices to Mariners of charts and these aids(Radar beacons)may be delayed until such time as they are assessed to be（）.

单项选择题 The external flotation bladder on an immersion suit should be inflated（）.

单项选择题 The Experimental Lighthouse-buoy has no navigational significance and may be removed at will.The above sentence means（）.