单项选择题 When the density of water is 1000,i.e.in fresh water and in summer zone a ship may load to the upper edge of the line marked（）.

单项选择题 When a ship in winter zone and in seawater of density1025,she must not load to more than the upper edge of the line marked（）.

单项选择题 When a ship is in summer zone and in seawater of density1025,she must not load to more than the upper edge of the line marked（）.