单项选择题
The external flotation bladder on an immersion suit should be inflated（）.
A.before you enter the water B.after you enter the water C.after one hour in the water D.after you notice that your suit is losing buoyancy
单项选择题 The Experimental Lighthouse-buoy has no navigational significance and may be removed at will.The above sentence means（）.
单项选择题 The effect of wind on exposed areas of the vessel is most noticeable when（）.
单项选择题 The diurnal variation of pressure is most noticeable（）.
